diff --git a/accessible/base/NotificationController.h b/accessible/base/NotificationController.h
index 137963f1170927ae0262e0dc26ef721d496376f4..41fa27bc4a3da41814a7f326792990df3424e81f 100644
--- a/accessible/base/NotificationController.h
+++ b/accessible/base/NotificationController.h
@@ -244,6 +244,8 @@ class NotificationController final : public EventQueue,
   }
 #endif
 
+  bool IsUpdatePendingForJugglerAccessibility() { return IsUpdatePending(); }
+
  protected:
   virtual ~NotificationController();
 
diff --git a/accessible/interfaces/nsIAccessibleDocument.idl b/accessible/interfaces/nsIAccessibleDocument.idl
index 1886621c373fe1fd5ff54092afc4c64e9ca9a8fd..a0febf72885410b45227171c63e823eca118cb37 100644
--- a/accessible/interfaces/nsIAccessibleDocument.idl
+++ b/accessible/interfaces/nsIAccessibleDocument.idl
@@ -67,4 +67,9 @@ interface nsIAccessibleDocument : nsISupports
    * Return the child document accessible at the given index.
    */
   nsIAccessibleDocument getChildDocumentAt(in unsigned long index);
+
+  /**
+   * Return whether it is updating.
+   */
+  readonly attribute boolean isUpdatePendingForJugglerAccessibility;
 };
diff --git a/accessible/xpcom/xpcAccessibleDocument.cpp b/accessible/xpcom/xpcAccessibleDocument.cpp
index d616e476b2149de5703077563680905e40db0459..7a8a48d5e7303a298a3e2e9fdf64558b3cdbe654 100644
--- a/accessible/xpcom/xpcAccessibleDocument.cpp
+++ b/accessible/xpcom/xpcAccessibleDocument.cpp
@@ -131,6 +131,13 @@ xpcAccessibleDocument::GetChildDocumentAt(uint32_t aIndex,
   return *aDocument ? NS_OK : NS_ERROR_INVALID_ARG;
 }
 
+NS_IMETHODIMP
+xpcAccessibleDocument::GetIsUpdatePendingForJugglerAccessibility(bool* updating) {
+  NS_ENSURE_ARG_POINTER(updating);
+  *updating = Intl()->Controller()->IsUpdatePendingForJugglerAccessibility();
+  return NS_OK;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // xpcAccessibleDocument
 
diff --git a/accessible/xpcom/xpcAccessibleDocument.h b/accessible/xpcom/xpcAccessibleDocument.h
index 8e9bf2b413585b5a3db9370eee5d57fb6c6716ed..5a3b194b54e3813c89989f13a214c989a409f0f6 100644
--- a/accessible/xpcom/xpcAccessibleDocument.h
+++ b/accessible/xpcom/xpcAccessibleDocument.h
@@ -47,6 +47,8 @@ class xpcAccessibleDocument : public xpcAccessibleHyperText,
   NS_IMETHOD GetChildDocumentAt(uint32_t aIndex,
                                 nsIAccessibleDocument** aDocument) final;
 
+  NS_IMETHOD GetIsUpdatePendingForJugglerAccessibility(bool* aUpdating) final;
+
   /**
    * Return XPCOM wrapper for the internal accessible.
    */
diff --git a/browser/app/winlauncher/LauncherProcessWin.cpp b/browser/app/winlauncher/LauncherProcessWin.cpp
index 8167d2b81c918e02ce757f7f448f22e07c29d140..3ae798880acfd8aa965ae08051f2f81855133711 100644
--- a/browser/app/winlauncher/LauncherProcessWin.cpp
+++ b/browser/app/winlauncher/LauncherProcessWin.cpp
@@ -23,6 +23,7 @@
 #include "mozilla/WinHeaderOnlyUtils.h"
 #include "nsWindowsHelpers.h"
 
+#include <io.h>
 #include <windows.h>
 #include <processthreadsapi.h>
 
@@ -422,8 +423,18 @@ Maybe<int> LauncherMain(int& argc, wchar_t* argv[],
   HANDLE stdHandles[] = {::GetStdHandle(STD_INPUT_HANDLE),
                          ::GetStdHandle(STD_OUTPUT_HANDLE),
                          ::GetStdHandle(STD_ERROR_HANDLE)};
-
   attrs.AddInheritableHandles(stdHandles);
+  // Playwright pipe installation.
+  bool hasJugglerPipe =
+      mozilla::CheckArg(argc, argv, "juggler-pipe", nullptr,
+                        mozilla::CheckArgFlag::None) == mozilla::ARG_FOUND;
+  if (hasJugglerPipe) {
+    intptr_t stdio3 = _get_osfhandle(3);
+    intptr_t stdio4 = _get_osfhandle(4);
+    HANDLE pipeHandles[] = {reinterpret_cast<HANDLE>(stdio3),
+                            reinterpret_cast<HANDLE>(stdio4)};
+    attrs.AddInheritableHandles(pipeHandles);
+  }
 
   DWORD creationFlags = CREATE_SUSPENDED | CREATE_UNICODE_ENVIRONMENT;
 
diff --git a/browser/installer/allowed-dupes.mn b/browser/installer/allowed-dupes.mn
index 213a99ed433d5219c2b9a64baad82d14cdbcd432..ee4f6484cdfe80899c28a1d9607494e520bfc93d 100644
--- a/browser/installer/allowed-dupes.mn
+++ b/browser/installer/allowed-dupes.mn
@@ -67,6 +67,12 @@ browser/features/webcompat@mozilla.org/shims/empty-shim.txt
 removed-files
 #endif
 
+# Juggler/marionette files
+chrome/juggler/content/content/floating-scrollbars.css
+browser/chrome/devtools/skin/floating-scrollbars-responsive-design.css
+chrome/juggler/content/server/stream-utils.js
+chrome/marionette/content/stream-utils.js
+
 # Bug 1606928 - There's no reliable way to connect Top Sites favicons with the favicons in the Search Service
 browser/chrome/browser/content/activity-stream/data/content/tippytop/favicons/allegro-pl.ico
 browser/defaults/settings/main/search-config-icons/96327a73-c433-5eb4-a16d-b090cadfb80b
diff --git a/browser/installer/package-manifest.in b/browser/installer/package-manifest.in
index 8aa6bf65634b6b82d448d57b337c3186bc6e5f96..49e98523b335d982a63863f6b93ae3db443fc925 100644
--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -196,6 +196,9 @@
 @RESPATH@/chrome/remote.manifest
 #endif
 
+@RESPATH@/chrome/juggler@JAREXT@
+@RESPATH@/chrome/juggler.manifest
+
 ; [Extensions]
 @RESPATH@/components/extensions-toolkit.manifest
 @RESPATH@/browser/components/extensions-browser.manifest
diff --git a/devtools/server/socket/websocket-server.js b/devtools/server/socket/websocket-server.js
index d49c6fbf1bf83b832795fa674f6b41f223eef812..7ea3540947ff5f61b15f27fbf4b955649f8e9ff9 100644
--- a/devtools/server/socket/websocket-server.js
+++ b/devtools/server/socket/websocket-server.js
@@ -134,13 +134,12 @@ function writeHttpResponse(output, response) {
  * Process the WebSocket handshake headers and return the key to be sent in
  * Sec-WebSocket-Accept response header.
  */
-function processRequest({ requestLine, headers }) {
+function processRequest({ requestLine, headers }, expectedPath) {
   const [method, path] = requestLine.split(" ");
   if (method !== "GET") {
     throw new Error("The handshake request must use GET method");
   }
-
-  if (path !== "/") {
+  if (path !== expectedPath) {
     throw new Error("The handshake request has unknown path");
   }
 
@@ -190,13 +189,13 @@ function computeKey(key) {
 /**
  * Perform the server part of a WebSocket opening handshake on an incoming connection.
  */
-const serverHandshake = async function (input, output) {
+const serverHandshake = async function (input, output, expectedPath) {
   // Read the request
   const request = await readHttpRequest(input);
 
   try {
     // Check and extract info from the request
-    const { acceptKey } = processRequest(request);
+    const { acceptKey } = processRequest(request, expectedPath);
 
     // Send response headers
     await writeHttpResponse(output, [
@@ -218,8 +217,8 @@ const serverHandshake = async function (input, output) {
  * Performs the WebSocket handshake and waits for the WebSocket to open.
  * Returns Promise with a WebSocket ready to send and receive messages.
  */
-const accept = async function (transport, input, output) {
-  await serverHandshake(input, output);
+const accept = async function (transport, input, output, expectedPath) {
+  await serverHandshake(input, output, expectedPath || "/");
 
   const transportProvider = {
     setListener(upgradeListener) {
diff --git a/docshell/base/BrowsingContext.cpp b/docshell/base/BrowsingContext.cpp
index 9b5c8143cb7f31a2eac982b0bbec4985816bdf5a..104ec4e5221af5647a776711fd349bbb0817aff4 100644
--- a/docshell/base/BrowsingContext.cpp
+++ b/docshell/base/BrowsingContext.cpp
@@ -106,8 +106,11 @@ struct ParamTraits<mozilla::dom::DisplayMode>
 
 template <>
 struct ParamTraits<mozilla::dom::PrefersColorSchemeOverride>
-    : public mozilla::dom::WebIDLEnumSerializer<
-          mozilla::dom::PrefersColorSchemeOverride> {};
+    : public mozilla::dom::WebIDLEnumSerializer<mozilla::dom::PrefersColorSchemeOverride> {};
+
+template <>
+struct ParamTraits<mozilla::dom::PrefersReducedMotionOverride>
+    : public mozilla::dom::WebIDLEnumSerializer<mozilla::dom::PrefersReducedMotionOverride> {};
 
 template <>
 struct ParamTraits<mozilla::dom::ForcedColorsOverride>
@@ -2865,6 +2868,23 @@ void BrowsingContext::DidSet(FieldIndex<IDX_ForcedColorsOverride>,
   PresContextAffectingFieldChanged();
 }
 
+void BrowsingContext::DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+                             dom::PrefersReducedMotionOverride aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (PrefersReducedMotionOverride() == aOldValue) {
+    return;
+  }
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    if (nsIDocShell* shell = aContext->GetDocShell()) {
+      if (nsPresContext* pc = shell->GetPresContext()) {
+        pc->MediaFeatureValuesChanged(
+            {MediaFeatureChangeReason::SystemMetricsChange},
+            MediaFeatureChangePropagation::JustThisDocument);
+      }
+    }
+  });
+}
+
 void BrowsingContext::DidSet(FieldIndex<IDX_MediumOverride>,
                              nsString&& aOldValue) {
   MOZ_ASSERT(IsTop());
diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
index 98a34cab1ffd393a5ee3cbca7799d024b3d4ac71..fdba3572ed3d2c7a6491c42ee535bf04a3585da4 100644
--- a/docshell/base/BrowsingContext.h
+++ b/docshell/base/BrowsingContext.h
@@ -203,10 +203,10 @@ struct EmbedderColorSchemes {
   FIELD(GVInaudibleAutoplayRequestStatus, GVAutoplayRequestStatus)            \
   /* ScreenOrientation-related APIs */                                        \
   FIELD(CurrentOrientationAngle, float)                                       \
-  FIELD(CurrentOrientationType, mozilla::dom::OrientationType)                \
+  FIELD(CurrentOrientationType, dom::OrientationType)                \
   FIELD(OrientationLock, mozilla::hal::ScreenOrientation)                     \
   FIELD(UserAgentOverride, nsString)                                          \
-  FIELD(TouchEventsOverrideInternal, mozilla::dom::TouchEventsOverride)       \
+  FIELD(TouchEventsOverrideInternal, dom::TouchEventsOverride)       \
   FIELD(EmbedderElementType, Maybe<nsString>)                                 \
   FIELD(MessageManagerGroup, nsString)                                        \
   FIELD(MaxTouchPointsOverride, uint8_t)                                      \
@@ -246,6 +246,8 @@ struct EmbedderColorSchemes {
    * <browser> embedder element. */                                           \
   FIELD(EmbedderColorSchemes, EmbedderColorSchemes)                           \
   FIELD(DisplayMode, dom::DisplayMode)                                        \
+  /* playwright addition */                                                   \
+  FIELD(PrefersReducedMotionOverride, dom::PrefersReducedMotionOverride)      \
   /* The number of entries added to the session history because of this       \
    * browsing context. */                                                     \
   FIELD(HistoryEntryCount, uint32_t)                                          \
@@ -946,6 +948,10 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
     return GetForcedColorsOverride();
   }
 
+  dom::PrefersReducedMotionOverride PrefersReducedMotionOverride() const {
+    return GetPrefersReducedMotionOverride();
+  }
+
   bool IsInBFCache() const;
 
   bool AllowJavascript() const { return GetAllowJavascript(); }
@@ -1125,6 +1131,15 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
   void WalkPresContexts(Callback&&);
   void PresContextAffectingFieldChanged();
 
+  bool CanSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride, ContentParent*) {
+    return IsTop();
+  }
+
+  void DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride aOldValue);
+
+
   void DidSet(FieldIndex<IDX_MediumOverride>, nsString&& aOldValue);
 
   bool CanSet(FieldIndex<IDX_SuspendMediaWhenInactive>, bool, ContentParent*) {
diff --git a/docshell/base/CanonicalBrowsingContext.cpp b/docshell/base/CanonicalBrowsingContext.cpp
index 57bd331851a3604a2d413bf2f0142532d341fa19..68dda8274473d99953d2bee0640d5bec5479827f 100644
--- a/docshell/base/CanonicalBrowsingContext.cpp
+++ b/docshell/base/CanonicalBrowsingContext.cpp
@@ -325,6 +325,8 @@ void CanonicalBrowsingContext::ReplacedBy(
   txn.SetShouldDelayMediaFromStart(GetShouldDelayMediaFromStart());
   txn.SetForceOffline(GetForceOffline());
   txn.SetTopInnerSizeForRFP(GetTopInnerSizeForRFP());
+  txn.SetPrefersReducedMotionOverride(GetPrefersReducedMotionOverride());
+  txn.SetForcedColorsOverride(GetForcedColorsOverride());
 
   // Propagate some settings on BrowsingContext replacement so they're not lost
   // on bfcached navigations. These are important for GeckoView (see bug
@@ -1610,6 +1612,12 @@ void CanonicalBrowsingContext::LoadURI(nsIURI* aURI,
     return;
   }
 
+  {
+    nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+    if (observerService) {
+      observerService->NotifyObservers(ToSupports(this), "juggler-navigation-started-browser", NS_ConvertASCIItoUTF16(nsPrintfCString("%" PRIu64, loadState->GetLoadIdentifier())).get());
+    }
+  }
   LoadURI(loadState, true);
 }
 
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 17f0d7fa7032a0aade92a8ecacd27017fea28a05..e1728e7cb162fcd96478050eab45ed439098c5b0 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -15,6 +15,12 @@
 #  include <unistd.h>  // for getpid()
 #endif
 
+#if JS_HAS_INTL_API && !MOZ_SYSTEM_ICU
+#  include "unicode/locid.h"
+#endif /* JS_HAS_INTL_API && !MOZ_SYSTEM_ICU */
+
+#include "js/LocaleSensitive.h"
+
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/AutoRestore.h"
@@ -66,6 +72,7 @@
 #include "mozilla/dom/DocGroup.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/FragmentDirective.h"
+#include "mozilla/dom/Geolocation.h"
 #include "mozilla/dom/HTMLAnchorElement.h"
 #include "mozilla/dom/HTMLIFrameElement.h"
 #include "mozilla/dom/PerformanceNavigation.h"
@@ -90,6 +97,7 @@
 #include "mozilla/dom/JSWindowActorChild.h"
 #include "mozilla/dom/DocumentBinding.h"
 #include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/dom/WorkerCommon.h"
 #include "mozilla/net/DocumentChannel.h"
 #include "mozilla/net/DocumentChannelChild.h"
 #include "mozilla/net/ParentChannelWrapper.h"
@@ -113,6 +121,7 @@
 #include "nsIDocumentViewer.h"
 #include "mozilla/dom/Document.h"
 #include "nsHTMLDocument.h"
+#include "mozilla/dom/Element.h"
 #include "nsIDocumentLoaderFactory.h"
 #include "nsIDOMWindow.h"
 #include "nsIEditingSession.h"
@@ -207,6 +216,7 @@
 #include "nsGlobalWindowInner.h"
 #include "nsGlobalWindowOuter.h"
 #include "nsJSEnvironment.h"
+#include "nsJSUtils.h"
 #include "nsNetCID.h"
 #include "nsNetUtil.h"
 #include "nsObjectLoadingContent.h"
@@ -347,6 +357,13 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
       mAllowDNSPrefetch(true),
       mAllowWindowControl(true),
       mCSSErrorReportingEnabled(false),
+      mFileInputInterceptionEnabled(false),
+      mOverrideHasFocus(false),
+      mBypassCSPEnabled(false),
+      mForceActiveState(false),
+      mDisallowBFCache(false),
+      mReducedMotionOverride(REDUCED_MOTION_OVERRIDE_NONE),
+      mForcedColorsOverride(FORCED_COLORS_OVERRIDE_NO_OVERRIDE),
       mAllowAuth(mItemType == typeContent),
       mAllowKeywordFixup(false),
       mDisableMetaRefreshWhenInactive(false),
@@ -3018,6 +3035,214 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
   return NS_OK;
 }
 
+// =============== Juggler Begin =======================
+
+nsDocShell* nsDocShell::GetRootDocShell() {
+  nsCOMPtr<nsIDocShellTreeItem> rootAsItem;
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(rootAsItem));
+  nsCOMPtr<nsIDocShell> rootShell = do_QueryInterface(rootAsItem);
+  return nsDocShell::Cast(rootShell);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetBypassCSPEnabled(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = mBypassCSPEnabled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetBypassCSPEnabled(bool aEnabled) {
+  mBypassCSPEnabled = aEnabled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetForceActiveState(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = mForceActiveState;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetForceActiveState(bool aEnabled) {
+  mForceActiveState = aEnabled;
+  ActivenessMaybeChanged();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDisallowBFCache(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = mDisallowBFCache;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetDisallowBFCache(bool aEnabled) {
+  mDisallowBFCache = aEnabled;
+  return NS_OK;
+}
+
+bool nsDocShell::IsBypassCSPEnabled() {
+  return GetRootDocShell()->mBypassCSPEnabled;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetOverrideHasFocus(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = mOverrideHasFocus;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetOverrideHasFocus(bool aEnabled) {
+  mOverrideHasFocus = aEnabled;
+  return NS_OK;
+}
+
+bool nsDocShell::ShouldOverrideHasFocus() const {
+  return mOverrideHasFocus;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetLanguageOverride(nsAString& aLanguageOverride) {
+  aLanguageOverride = GetRootDocShell()->mLanguageOverride;
+  return NS_OK;
+}
+
+
+static void SetIcuLocale(const nsAString& aLanguageOverride) {
+  icu::Locale locale(NS_LossyConvertUTF16toASCII(aLanguageOverride).get());
+  if (icu::Locale::getDefault() != locale) {
+    UErrorCode error_code = U_ZERO_ERROR;
+    const char* lang = locale.getLanguage();
+    if (lang != nullptr && *lang != '\0') {
+      icu::Locale::setDefault(locale, error_code);
+    } else {
+      fprintf(stderr, "SetIcuLocale Failed to set the ICU default locale to %s\n", NS_LossyConvertUTF16toASCII(aLanguageOverride).get());
+    }
+  }
+
+  AutoJSAPI jsapi;
+  jsapi.Init();
+  JSContext* cx = jsapi.cx();
+  JS_ResetDefaultLocale(JS_GetRuntime(cx));
+
+  ResetDefaultLocaleInAllWorkers();
+}
+
+NS_IMETHODIMP
+nsDocShell::SetLanguageOverride(const nsAString& aLanguageOverride) {
+  mLanguageOverride = aLanguageOverride;
+  SetIcuLocale(aLanguageOverride);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::OverrideTimezone(const nsAString& aTimezoneOverride,
+                             bool* aSuccess) {
+  NS_ENSURE_ARG(aSuccess);
+  NS_LossyConvertUTF16toASCII timeZoneId(aTimezoneOverride);
+  *aSuccess = nsJSUtils::SetTimeZoneOverride(timeZoneId.get());
+
+  // Set TZ which affects localtime_s().
+  auto setTimeZoneEnv = [](const char* value) {
+#if defined(_WIN32)
+    return _putenv_s("TZ", value) == 0;
+#else
+    return setenv("TZ", value, true) == 0;
+#endif /* _WIN32 */
+  };
+  if (*aSuccess) {
+    *aSuccess = setTimeZoneEnv(timeZoneId.get());
+    if (!*aSuccess) {
+      fprintf(stderr, "Failed to set 'TZ' to '%s'\n", timeZoneId.get());
+    }
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetFileInputInterceptionEnabled(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = GetRootDocShell()->mFileInputInterceptionEnabled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetFileInputInterceptionEnabled(bool aEnabled) {
+  mFileInputInterceptionEnabled = aEnabled;
+  return NS_OK;
+}
+
+bool nsDocShell::IsFileInputInterceptionEnabled() {
+  return GetRootDocShell()->mFileInputInterceptionEnabled;
+}
+
+void nsDocShell::FilePickerShown(mozilla::dom::Element* element) {
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  observerService->NotifyObservers(
+      ToSupports(element), "juggler-file-picker-shown", nullptr);
+}
+
+RefPtr<nsGeolocationService> nsDocShell::GetGeolocationServiceOverride() {
+  return GetRootDocShell()->mGeolocationServiceOverride;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetGeolocationOverride(nsIDOMGeoPosition* aGeolocationOverride) {
+  if (aGeolocationOverride) {
+    if (!mGeolocationServiceOverride) {
+      mGeolocationServiceOverride = new nsGeolocationService();
+      mGeolocationServiceOverride->Init();
+    }
+    mGeolocationServiceOverride->Update(aGeolocationOverride);
+  } else {
+    mGeolocationServiceOverride = nullptr;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetReducedMotionOverride(ReducedMotionOverride* aReducedMotionOverride) {
+  *aReducedMotionOverride = GetRootDocShell()->mReducedMotionOverride;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetReducedMotionOverride(ReducedMotionOverride aReducedMotionOverride) {
+  mReducedMotionOverride = aReducedMotionOverride;
+  RefPtr<nsPresContext> presContext = GetPresContext();
+  if (presContext) {
+    presContext->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::SystemMetricsChange},
+        MediaFeatureChangePropagation::JustThisDocument);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetForcedColorsOverride(ForcedColorsOverride* aForcedColorsOverride) {
+  *aForcedColorsOverride = GetRootDocShell()->mForcedColorsOverride;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetForcedColorsOverride(ForcedColorsOverride aForcedColorsOverride) {
+  mForcedColorsOverride = aForcedColorsOverride;
+  RefPtr<nsPresContext> presContext = GetPresContext();
+  if (presContext) {
+    presContext->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::SystemMetricsChange},
+        MediaFeatureChangePropagation::JustThisDocument);
+  }
+  return NS_OK;
+}
+
+// =============== Juggler End =======================
+
 NS_IMETHODIMP
 nsDocShell::GetIsNavigating(bool* aOut) {
   *aOut = mIsNavigating;
@@ -4714,7 +4939,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
 }
 
 void nsDocShell::ActivenessMaybeChanged() {
-  const bool isActive = mBrowsingContext->IsActive();
+  const bool isActive = mForceActiveState || mBrowsingContext->IsActive();
   if (RefPtr<PresShell> presShell = GetPresShell()) {
     presShell->ActivenessMaybeChanged();
   }
@@ -6641,6 +6866,10 @@ bool nsDocShell::CanSavePresentation(uint32_t aLoadType,
     return false;  // no entry to save into
   }
 
+  if (mDisallowBFCache) {
+    return false;
+  }
+
   MOZ_ASSERT(!mozilla::SessionHistoryInParent(),
              "mOSHE cannot be non-null with SHIP");
   nsCOMPtr<nsIDocumentViewer> viewer = mOSHE->GetDocumentViewer();
@@ -8373,6 +8602,12 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
                      true,  // aForceNoOpener
                      getter_AddRefs(newBC));
       MOZ_ASSERT(!newBC);
+      if (rv == NS_OK) {
+        nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+        if (observerService) {
+          observerService->NotifyObservers(GetAsSupports(this), "juggler-window-open-in-new-context", nullptr);
+        }
+      }
       return rv;
     }
 
@@ -9520,6 +9755,16 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
                    nsINetworkPredictor::PREDICT_LOAD, attrs, nullptr);
 
   nsCOMPtr<nsIRequest> req;
+
+  // Juggler: report navigation started for non-same-document and non-javascript
+  // navigations.
+  if (!isJavaScript && !sameDocument) {
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+    if (observerService) {
+      observerService->NotifyObservers(GetAsSupports(this), "juggler-navigation-started-renderer", NS_ConvertASCIItoUTF16(nsPrintfCString("%" PRIu64, aLoadState->GetLoadIdentifier())).get());
+    }
+  }
   rv = DoURILoad(aLoadState, aCacheKey, getter_AddRefs(req));
 
   if (NS_SUCCEEDED(rv)) {
@@ -12724,6 +12969,9 @@ class OnLinkClickEvent : public Runnable {
       mHandler->OnLinkClickSync(mContent, mLoadState, mNoOpenerImplied,
                                 mTriggeringPrincipal);
     }
+    nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+    observerService->NotifyObservers(ToSupports(mContent), "juggler-link-click-sync", nullptr);
+
     return NS_OK;
   }
 
@@ -12813,6 +13061,8 @@ nsresult nsDocShell::OnLinkClick(
   nsCOMPtr<nsIRunnable> ev =
       new OnLinkClickEvent(this, aContent, loadState, noOpenerImplied,
                            aIsTrusted, aTriggeringPrincipal);
+  nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+  observerService->NotifyObservers(ToSupports(aContent), "juggler-link-click", nullptr);
   return Dispatch(ev.forget());
 }
 
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index 0cf72f8fffb40a4205f9d2cb339f4ebd9031373f..0b09b2877781d0693d466b66e6ff00872988af4a 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -15,6 +15,7 @@
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"
 #include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/WindowProxyHolder.h"
 #include "nsCOMPtr.h"
 #include "nsCharsetSource.h"
@@ -76,6 +77,7 @@ class nsCommandManager;
 class nsDocShellEditorData;
 class nsDOMNavigationTiming;
 class nsDSURIContentListener;
+class nsGeolocationService;
 class nsGlobalWindowOuter;
 
 class FramingChecker;
@@ -403,6 +405,15 @@ class nsDocShell final : public nsDocLoader,
   void SetWillChangeProcess() { mWillChangeProcess = true; }
   bool WillChangeProcess() { return mWillChangeProcess; }
 
+  bool IsFileInputInterceptionEnabled();
+  void FilePickerShown(mozilla::dom::Element* element);
+
+  bool ShouldOverrideHasFocus() const;
+
+  bool IsBypassCSPEnabled();
+
+  RefPtr<nsGeolocationService> GetGeolocationServiceOverride();
+
   // Create a content viewer within this nsDocShell for the given
   // `WindowGlobalChild` actor.
   nsresult CreateDocumentViewerForActor(
@@ -1006,6 +1017,8 @@ class nsDocShell final : public nsDocLoader,
 
   bool CSSErrorReportingEnabled() const { return mCSSErrorReportingEnabled; }
 
+  nsDocShell* GetRootDocShell();
+
   // Handles retrieval of subframe session history for nsDocShell::LoadURI. If a
   // load is requested in a subframe of the current DocShell, the subframe
   // loadType may need to reflect the loadType of the parent document, or in
@@ -1283,6 +1296,16 @@ class nsDocShell final : public nsDocLoader,
   bool mAllowDNSPrefetch : 1;
   bool mAllowWindowControl : 1;
   bool mCSSErrorReportingEnabled : 1;
+  bool mFileInputInterceptionEnabled: 1;
+  bool mOverrideHasFocus : 1;
+  bool mBypassCSPEnabled : 1;
+  bool mForceActiveState : 1;
+  bool mDisallowBFCache : 1;
+  nsString mLanguageOverride;
+  RefPtr<nsGeolocationService> mGeolocationServiceOverride;
+  ReducedMotionOverride mReducedMotionOverride;
+  ForcedColorsOverride mForcedColorsOverride;
+
   bool mAllowAuth : 1;
   bool mAllowKeywordFixup : 1;
   bool mDisableMetaRefreshWhenInactive : 1;
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index fdc04f16c6f547077ad8c872f9357d85d4513c50..199f8fdb0670265c715f99f5cac1a2b2f22c963d 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -44,6 +44,7 @@ interface nsIURI;
 interface nsIChannel;
 interface nsIContentSecurityPolicy;
 interface nsIDocumentViewer;
+interface nsIDOMGeoPosition;
 interface nsIEditor;
 interface nsIEditingSession;
 interface nsIInputStream;
@@ -719,6 +720,36 @@ interface nsIDocShell : nsIDocShellTreeItem
    */
   void synchronizeLayoutHistoryState();
 
+  attribute boolean fileInputInterceptionEnabled;
+
+  attribute boolean overrideHasFocus;
+
+  attribute boolean bypassCSPEnabled;
+
+  attribute boolean forceActiveState;
+
+  attribute boolean disallowBFCache;
+
+  attribute AString languageOverride;
+
+  boolean overrideTimezone(in AString timezoneId);
+
+  cenum ReducedMotionOverride : 8 {
+    REDUCED_MOTION_OVERRIDE_REDUCE,
+    REDUCED_MOTION_OVERRIDE_NO_PREFERENCE,
+    REDUCED_MOTION_OVERRIDE_NONE, /* This clears the override. */
+  };
+  [infallible] attribute nsIDocShell_ReducedMotionOverride reducedMotionOverride;
+
+  cenum ForcedColorsOverride : 8 {
+    FORCED_COLORS_OVERRIDE_ACTIVE,
+    FORCED_COLORS_OVERRIDE_NONE,
+    FORCED_COLORS_OVERRIDE_NO_OVERRIDE, /* This clears the override. */
+  };
+  [infallible] attribute nsIDocShell_ForcedColorsOverride forcedColorsOverride;
+
+  void setGeolocationOverride(in nsIDOMGeoPosition position);
+
   /**
    * This attempts to save any applicable layout history state (like
    * scroll position) in the nsISHEntry. This is normally done
diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
index b460181916b4f4edfc1a56e8b06f6506bd81465b..2a493209a2667ad8c5e84b893b5ce01d0dcc3fee 100644
--- a/dom/base/Document.cpp
+++ b/dom/base/Document.cpp
@@ -3745,6 +3745,9 @@ void Document::SendToConsole(nsCOMArray<nsISecurityConsoleMessage>& aMessages) {
 }
 
 void Document::ApplySettingsFromCSP(bool aSpeculative) {
+  if (mDocumentContainer && mDocumentContainer->IsBypassCSPEnabled())
+    return;
+
   nsresult rv = NS_OK;
   if (!aSpeculative) {
     // 1) apply settings from regular CSP
@@ -3802,6 +3805,11 @@ nsresult Document::InitCSP(nsIChannel* aChannel) {
   MOZ_ASSERT(!mScriptGlobalObject,
              "CSP must be initialized before mScriptGlobalObject is set!");
 
+  nsCOMPtr<nsIDocShell> shell(mDocumentContainer);
+  if (shell && nsDocShell::Cast(shell)->IsBypassCSPEnabled()) {
+    return NS_OK;
+  }
+
   // If this is a data document - no need to set CSP.
   if (mLoadedAsData) {
     return NS_OK;
@@ -4603,6 +4611,10 @@ bool Document::HasFocus(ErrorResult& rv) const {
     return false;
   }
 
+  if (IsActive() && mDocumentContainer->ShouldOverrideHasFocus()) {
+    return true;
+  }
+
   if (!fm->IsInActiveWindow(bc)) {
     return false;
   }
@@ -19462,6 +19474,35 @@ ColorScheme Document::PreferredColorScheme(IgnoreRFP aIgnoreRFP) const {
   return PreferenceSheet::PrefsFor(*this).mColorScheme;
 }
 
+bool Document::PrefersReducedMotion() const {
+  auto* docShell = static_cast<nsDocShell*>(GetDocShell());
+  nsIDocShell::ReducedMotionOverride reducedMotion;
+  if (docShell && docShell->GetReducedMotionOverride(&reducedMotion) == NS_OK &&
+      reducedMotion != nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE) {
+    switch (reducedMotion) {
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_REDUCE:
+        return true;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NO_PREFERENCE:
+        return false;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE:
+        break;
+    };
+  }
+
+  if (auto* bc = GetBrowsingContext()) {
+    switch (bc->Top()->PrefersReducedMotionOverride()) {
+      case dom::PrefersReducedMotionOverride::Reduce:
+        return true;
+      case dom::PrefersReducedMotionOverride::No_preference:
+        return false;
+      case dom::PrefersReducedMotionOverride::None:
+        break;
+    }
+  }
+
+  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+}
+
 bool Document::HasRecentlyStartedForegroundLoads() {
   if (!sLoadingForegroundTopLevelContentDocument) {
     return false;
diff --git a/dom/base/Document.h b/dom/base/Document.h
index 9b748acbce8e4dd1c1393aa5d26170747ec48228..a8bc4c52651ea32128388d1e5f486b7fe0203d4b 100644
--- a/dom/base/Document.h
+++ b/dom/base/Document.h
@@ -4108,6 +4108,8 @@ class Document : public nsINode,
   // color-scheme meta tag.
   ColorScheme DefaultColorScheme() const;
 
+  bool PrefersReducedMotion() const;
+
   static bool HasRecentlyStartedForegroundLoads();
 
   static bool AutomaticStorageAccessPermissionCanBeGranted(
diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
index d7ed73aee3af96096e36ead6d1aeecec7269556d..b2f3b53f46bfbcca044a7d9f18a694469b4884d5 100644
--- a/dom/base/Navigator.cpp
+++ b/dom/base/Navigator.cpp
@@ -344,14 +344,18 @@ void Navigator::GetAppName(nsAString& aAppName) const {
  * for more detail.
  */
 /* static */
-void Navigator::GetAcceptLanguages(nsTArray<nsString>& aLanguages) {
+void Navigator::GetAcceptLanguages(const nsString* aLanguageOverride, nsTArray<nsString>& aLanguages) {
   MOZ_ASSERT(NS_IsMainThread());
 
   aLanguages.Clear();
 
   // E.g. "de-de, en-us,en".
   nsAutoString acceptLang;
-  Preferences::GetLocalizedString("intl.accept_languages", acceptLang);
+  if (aLanguageOverride && aLanguageOverride->Length())
+    acceptLang = *aLanguageOverride;
+  else
+    Preferences::GetLocalizedString("intl.accept_languages", acceptLang);
+    
 
   // Split values on commas.
   for (nsDependentSubstring lang :
@@ -403,7 +407,13 @@ void Navigator::GetLanguage(nsAString& aLanguage) {
 }
 
 void Navigator::GetLanguages(nsTArray<nsString>& aLanguages) {
-  GetAcceptLanguages(aLanguages);
+  if (mWindow && mWindow->GetDocShell()) {
+    nsString languageOverride;
+    mWindow->GetDocShell()->GetLanguageOverride(languageOverride);
+    GetAcceptLanguages(&languageOverride, aLanguages);
+  } else {
+    GetAcceptLanguages(nullptr, aLanguages);
+  }
 
   // The returned value is cached by the binding code. The window listens to the
   // accept languages change and will clear the cache when needed. It has to
@@ -2298,7 +2308,8 @@ bool Navigator::Webdriver() {
   }
 #endif
 
-  return false;
+  // Playwright is automating the browser, so we should pretend to be a webdriver
+  return true;
 }
 
 AutoplayPolicy Navigator::GetAutoplayPolicy(AutoplayPolicyMediaType aType) {
diff --git a/dom/base/Navigator.h b/dom/base/Navigator.h
index 6abf6cef230c97815f17f6b7abf9f1b1de274a6f..46ead1f32e0d710b5b32e61dff72a4f772d5421e 100644
--- a/dom/base/Navigator.h
+++ b/dom/base/Navigator.h
@@ -218,7 +218,7 @@ class Navigator final : public nsISupports, public nsWrapperCache {
 
   StorageManager* Storage();
 
-  static void GetAcceptLanguages(nsTArray<nsString>& aLanguages);
+  static void GetAcceptLanguages(const nsString* aLanguageOverride, nsTArray<nsString>& aLanguages);
 
   dom::MediaCapabilities* MediaCapabilities();
   dom::MediaSession* MediaSession();
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 80df23b73f132c2b6ec99df1cb219878d6ea8639..0b82f7117805f0ad5ccca21532f87852eaae3ecf 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -8793,7 +8793,8 @@ nsresult nsContentUtils::SendMouseEvent(
     bool aIgnoreRootScrollFrame, float aPressure,
     unsigned short aInputSourceArg, uint32_t aIdentifier, bool aToWindow,
     PreventDefaultResult* aPreventDefault, bool aIsDOMEventSynthesized,
-    bool aIsWidgetEventSynthesized) {
+    bool aIsWidgetEventSynthesized,
+    bool convertToPointer, uint32_t aJugglerEventId) {
   nsPoint offset;
   nsCOMPtr<nsIWidget> widget = GetWidget(aPresShell, &offset);
   if (!widget) return NS_ERROR_FAILURE;
@@ -8801,6 +8802,7 @@ nsresult nsContentUtils::SendMouseEvent(
   EventMessage msg;
   Maybe<WidgetMouseEvent::ExitFrom> exitFrom;
   bool contextMenuKey = false;
+  bool isPWDragEventMessage = false;
   if (aType.EqualsLiteral("mousedown")) {
     msg = eMouseDown;
   } else if (aType.EqualsLiteral("mouseup")) {
@@ -8826,6 +8828,12 @@ nsresult nsContentUtils::SendMouseEvent(
     msg = eMouseHitTest;
   } else if (aType.EqualsLiteral("MozMouseExploreByTouch")) {
     msg = eMouseExploreByTouch;
+  } else if (aType.EqualsLiteral("dragover")) {
+    msg = eDragOver;
+    isPWDragEventMessage = true;
+  } else if (aType.EqualsLiteral("drop")) {
+    msg = eDrop;
+    isPWDragEventMessage = true;
   } else {
     return NS_ERROR_FAILURE;
   }
@@ -8836,7 +8844,14 @@ nsresult nsContentUtils::SendMouseEvent(
 
   Maybe<WidgetPointerEvent> pointerEvent;
   Maybe<WidgetMouseEvent> mouseEvent;
-  if (IsPointerEventMessage(msg)) {
+  Maybe<WidgetDragEvent> pwDragEvent;
+
+  if (isPWDragEventMessage) {
+    pwDragEvent.emplace(true, msg, widget);
+    pwDragEvent->mReason = aIsWidgetEventSynthesized
+                             ? WidgetMouseEvent::eSynthesized
+                             : WidgetMouseEvent::eReal;
+  } else if (IsPointerEventMessage(msg)) {
     MOZ_ASSERT(!aIsWidgetEventSynthesized,
                "The event shouldn't be dispatched as a synthesized event");
     if (MOZ_UNLIKELY(aIsWidgetEventSynthesized)) {
@@ -8855,8 +8870,11 @@ nsresult nsContentUtils::SendMouseEvent(
                        contextMenuKey ? WidgetMouseEvent::eContextMenuKey
                                       : WidgetMouseEvent::eNormal);
   }
+
   WidgetMouseEvent& mouseOrPointerEvent =
+      pwDragEvent.isSome() ? pwDragEvent.ref() :
       pointerEvent.isSome() ? pointerEvent.ref() : mouseEvent.ref();
+
   mouseOrPointerEvent.pointerId = aIdentifier;
   mouseOrPointerEvent.mModifiers = GetWidgetModifiers(aModifiers);
   mouseOrPointerEvent.mButton = aButton;
@@ -8869,6 +8887,8 @@ nsresult nsContentUtils::SendMouseEvent(
   mouseOrPointerEvent.mClickCount = aClickCount;
   mouseOrPointerEvent.mFlags.mIsSynthesizedForTests = aIsDOMEventSynthesized;
   mouseOrPointerEvent.mExitFrom = exitFrom;
+  mouseOrPointerEvent.mJugglerEventId = aJugglerEventId;
+  mouseOrPointerEvent.convertToPointer = convertToPointer;
 
   nsPresContext* presContext = aPresShell->GetPresContext();
   if (!presContext) return NS_ERROR_FAILURE;
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index d9556910b2e27aebd648835353a6843347d6f8ac..61fdbfda2c43e3265fa8bc48a1d0f5f38f70b48c 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -3039,7 +3039,8 @@ class nsContentUtils {
       int32_t aModifiers, bool aIgnoreRootScrollFrame, float aPressure,
       unsigned short aInputSourceArg, uint32_t aIdentifier, bool aToWindow,
       mozilla::PreventDefaultResult* aPreventDefault,
-      bool aIsDOMEventSynthesized, bool aIsWidgetEventSynthesized);
+      bool aIsDOMEventSynthesized, bool aIsWidgetEventSynthesized,
+      bool convertToPointer = true, uint32_t aJugglerEventId = 0);
 
   static void FirePageShowEventForFrameLoaderSwap(
       nsIDocShellTreeItem* aItem,
diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index 7e22693477bb4ededfc3fff568f3993db6abb838..91379e3032b64e08892790a72c6cc421983cf94e 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -685,6 +685,26 @@ nsDOMWindowUtils::GetPresShellId(uint32_t* aPresShellId) {
   return NS_ERROR_FAILURE;
 }
 
+static uint32_t sJugglerEventId = 1000;
+
+NS_IMETHODIMP
+nsDOMWindowUtils::JugglerSendMouseEvent(
+    const nsAString& aType, float aX, float aY, int32_t aButton,
+    int32_t aClickCount, int32_t aModifiers, bool aIgnoreRootScrollFrame,
+    float aPressure, unsigned short aInputSourceArg,
+    bool aIsDOMEventSynthesized, bool aIsWidgetEventSynthesized,
+    int32_t aButtons, uint32_t aIdentifier, bool aDisablePointerEvent,
+    uint32_t* aJugglerEventId) {
+  *aJugglerEventId = ++sJugglerEventId;
+  return SendMouseEventCommon(
+      aType, aX, aY, aButton, aClickCount, aModifiers, aIgnoreRootScrollFrame,
+      aPressure, aInputSourceArg,
+      aIdentifier, false,
+      nullptr, aIsDOMEventSynthesized,
+      aIsWidgetEventSynthesized,
+      aButtons, !aDisablePointerEvent, *aJugglerEventId);
+}
+
 NS_IMETHODIMP
 nsDOMWindowUtils::SendMouseEvent(
     const nsAString& aType, float aX, float aY, int32_t aButton,
@@ -699,7 +719,7 @@ nsDOMWindowUtils::SendMouseEvent(
       aOptionalArgCount >= 7 ? aIdentifier : DEFAULT_MOUSE_POINTER_ID, false,
       aPreventDefault, aOptionalArgCount >= 4 ? aIsDOMEventSynthesized : true,
       aOptionalArgCount >= 5 ? aIsWidgetEventSynthesized : false,
-      aOptionalArgCount >= 6 ? aButtons : MOUSE_BUTTONS_NOT_SPECIFIED);
+      aOptionalArgCount >= 6 ? aButtons : MOUSE_BUTTONS_NOT_SPECIFIED, true, 0);
 }
 
 NS_IMETHODIMP
@@ -717,7 +737,7 @@ nsDOMWindowUtils::SendMouseEventToWindow(
       aOptionalArgCount >= 7 ? aIdentifier : DEFAULT_MOUSE_POINTER_ID, true,
       nullptr, aOptionalArgCount >= 4 ? aIsDOMEventSynthesized : true,
       aOptionalArgCount >= 5 ? aIsWidgetEventSynthesized : false,
-      aOptionalArgCount >= 6 ? aButtons : MOUSE_BUTTONS_NOT_SPECIFIED);
+      aOptionalArgCount >= 6 ? aButtons : MOUSE_BUTTONS_NOT_SPECIFIED, 0);
 }
 
 NS_IMETHODIMP
@@ -726,13 +746,13 @@ nsDOMWindowUtils::SendMouseEventCommon(
     int32_t aClickCount, int32_t aModifiers, bool aIgnoreRootScrollFrame,
     float aPressure, unsigned short aInputSourceArg, uint32_t aPointerId,
     bool aToWindow, bool* aPreventDefault, bool aIsDOMEventSynthesized,
-    bool aIsWidgetEventSynthesized, int32_t aButtons) {
+    bool aIsWidgetEventSynthesized, int32_t aButtons, bool aConvertToPointer, uint32_t aJugglerEventId) {
   RefPtr<PresShell> presShell = GetPresShell();
   PreventDefaultResult preventDefaultResult;
   nsresult rv = nsContentUtils::SendMouseEvent(
       presShell, aType, aX, aY, aButton, aButtons, aClickCount, aModifiers,
       aIgnoreRootScrollFrame, aPressure, aInputSourceArg, aPointerId, aToWindow,
-      &preventDefaultResult, aIsDOMEventSynthesized, aIsWidgetEventSynthesized);
+      &preventDefaultResult, aIsDOMEventSynthesized, aIsWidgetEventSynthesized, aConvertToPointer, aJugglerEventId);
 
   if (aPreventDefault) {
     *aPreventDefault = preventDefaultResult != PreventDefaultResult::No;
diff --git a/dom/base/nsDOMWindowUtils.h b/dom/base/nsDOMWindowUtils.h
index 47ff326b202266b1d7d6af8bdfb72776df8a6a93..b8e084b0c788c46345b1455b8257f1719c851404 100644
--- a/dom/base/nsDOMWindowUtils.h
+++ b/dom/base/nsDOMWindowUtils.h
@@ -93,7 +93,7 @@ class nsDOMWindowUtils final : public nsIDOMWindowUtils,
       int32_t aClickCount, int32_t aModifiers, bool aIgnoreRootScrollFrame,
       float aPressure, unsigned short aInputSourceArg, uint32_t aIdentifier,
       bool aToWindow, bool* aPreventDefault, bool aIsDOMEventSynthesized,
-      bool aIsWidgetEventSynthesized, int32_t aButtons);
+      bool aIsWidgetEventSynthesized, int32_t aButtons, bool aConvertToPointer = true, uint32_t aJugglerEventId = 0);
 
   MOZ_CAN_RUN_SCRIPT
   nsresult SendTouchEventCommon(
diff --git a/dom/base/nsFocusManager.cpp b/dom/base/nsFocusManager.cpp
index f24942e513f85a0f750eabaeb429889a9cf99092..74683b60bdfac459c0047c52b7efefa9aae1c01a 100644
--- a/dom/base/nsFocusManager.cpp
+++ b/dom/base/nsFocusManager.cpp
@@ -1712,6 +1712,10 @@ Maybe<uint64_t> nsFocusManager::SetFocusInner(Element* aNewContent,
         (GetActiveBrowsingContext() == newRootBrowsingContext);
   }
 
+  // In Playwright, we want to send focus events even if the element
+  // isn't actually in the active window.
+  isElementInActiveWindow = true;
+
   // Exit fullscreen if a website focuses another window
   if (StaticPrefs::full_screen_api_exit_on_windowRaise() &&
       !isElementInActiveWindow && (aFlags & FLAG_RAISE)) {
@@ -2297,6 +2301,7 @@ bool nsFocusManager::BlurImpl(BrowsingContext* aBrowsingContextToClear,
                               bool aIsLeavingDocument, bool aAdjustWidget,
                               bool aRemainActive, Element* aElementToFocus,
                               uint64_t aActionId) {
+
   LOGFOCUS(("<<Blur begin actionid: %" PRIu64 ">>", aActionId));
 
   // hold a reference to the focused content, which may be null
@@ -2343,6 +2348,11 @@ bool nsFocusManager::BlurImpl(BrowsingContext* aBrowsingContextToClear,
     return true;
   }
 
+  // Playwright: emulate focused page by never bluring when leaving document.
+  if (XRE_IsContentProcess() && aIsLeavingDocument && docShell && nsDocShell::Cast(docShell)->ShouldOverrideHasFocus()) {
+    return true;
+  }
+
   // Keep a ref to presShell since dispatching the DOM event may cause
   // the document to be destroyed.
   RefPtr<PresShell> presShell = docShell->GetPresShell();
@@ -3020,7 +3030,9 @@ void nsFocusManager::RaiseWindow(nsPIDOMWindowOuter* aWindow,
     }
   }
 
-  if (sTestMode) {
+  // In Playwright, we still want to execte the embedder functions
+  // to actually show / focus windows.
+  if (false && sTestMode) {
     // In test mode, emulate raising the window. WindowRaised takes
     // care of lowering the present active window. This happens in
     // a separate runnable to avoid touching multiple windows in
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index 8973a1e401670d32808136d47ab8efb0e396a549..0889b2ff12540c9aa36d9efc5d81fb684513b686 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -2516,10 +2516,16 @@ nsresult nsGlobalWindowOuter::SetNewDocument(Document* aDocument,
     }();
 
     if (!isContentAboutBlankInChromeDocshell) {
-      newInnerWindow->mHasNotifiedGlobalCreated = true;
-      nsContentUtils::AddScriptRunner(NewRunnableMethod(
-          "nsGlobalWindowOuter::DispatchDOMWindowCreated", this,
-          &nsGlobalWindowOuter::DispatchDOMWindowCreated));
+      if (!newInnerWindow->mHasNotifiedGlobalCreated) {
+        newInnerWindow->mHasNotifiedGlobalCreated = true;
+        nsContentUtils::AddScriptRunner(NewRunnableMethod(
+            "nsGlobalWindowOuter::DispatchDOMWindowCreated", this,
+            &nsGlobalWindowOuter::DispatchDOMWindowCreated));
+      } else if (!reUseInnerWindow) {
+        nsContentUtils::AddScriptRunner(NewRunnableMethod(
+            "nsGlobalWindowOuter::JugglerDispatchDOMWindowReused", this,
+            &nsGlobalWindowOuter::JugglerDispatchDOMWindowReused));
+      }
     }
   }
 
@@ -2639,6 +2645,19 @@ void nsGlobalWindowOuter::DispatchDOMWindowCreated() {
   }
 }
 
+void nsGlobalWindowOuter::JugglerDispatchDOMWindowReused() {
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (observerService && mDoc) {
+    nsIPrincipal* principal = mDoc->NodePrincipal();
+    if (!principal->IsSystemPrincipal()) {
+      observerService->NotifyObservers(static_cast<nsIDOMWindow*>(this),
+                                      "juggler-dom-window-reused",
+                                      nullptr);
+    }
+  }
+}
+
 void nsGlobalWindowOuter::ClearStatus() { SetStatusOuter(u""_ns); }
 
 void nsGlobalWindowOuter::SetDocShell(nsDocShell* aDocShell) {
diff --git a/dom/base/nsGlobalWindowOuter.h b/dom/base/nsGlobalWindowOuter.h
index b388bfb6ea26a88c29d9d14dfbc375ff7bd09eec..8685e4cece9d2cc2511b9d3022c891df6dc1660d 100644
--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -317,6 +317,7 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
 
   // Outer windows only.
   void DispatchDOMWindowCreated();
+  void JugglerDispatchDOMWindowReused();
 
   // Outer windows only.
   virtual void EnsureSizeAndPositionUpToDate() override;
diff --git a/dom/base/nsINode.cpp b/dom/base/nsINode.cpp
index 03990e9ed30f4dfa7d3dbec40942ce1121b07b8d..2dd4ac45ad0aec598ad9c00e6e280757b33c7648 100644
--- a/dom/base/nsINode.cpp
+++ b/dom/base/nsINode.cpp
@@ -1426,6 +1426,61 @@ void nsINode::GetBoxQuadsFromWindowOrigin(const BoxQuadOptions& aOptions,
   mozilla::GetBoxQuadsFromWindowOrigin(this, aOptions, aResult, aRv);
 }
 
+static nsIFrame* GetFirstFrame(nsINode* aNode) {
+  if (!aNode->IsContent())
+    return nullptr;
+  nsIFrame* frame = aNode->AsContent()->GetPrimaryFrame(FlushType::Frames);
+  if (!frame) {
+    FlattenedChildIterator iter(aNode->AsContent());
+    for (nsIContent* child = iter.GetNextChild(); child; child = iter.GetNextChild()) {
+      frame = child->GetPrimaryFrame(FlushType::Frames);
+      if (frame) {
+        break;
+      }
+    }
+  }
+  return frame;
+}
+
+void nsINode::ScrollRectIntoViewIfNeeded(int32_t x, int32_t y,
+                                         int32_t w, int32_t h,
+                                         ErrorResult& aRv) {
+  aRv = NS_ERROR_UNEXPECTED;
+  nsCOMPtr<Document> document = OwnerDoc();
+  if (!document) {
+    return aRv.ThrowNotFoundError("Node is detached from document");
+  }
+  PresShell* presShell = document->GetPresShell();
+  if (!presShell) {
+    return aRv.ThrowNotFoundError("Node is detached from document");
+  }
+  nsIFrame* primaryFrame = GetFirstFrame(this);
+  if (!primaryFrame) {
+    return aRv.ThrowNotFoundError("Node does not have a layout object");
+  }
+  aRv = NS_OK;
+  nsRect rect;
+  if (x == -1 && y == -1 && w == -1 && h == -1) {
+    rect = primaryFrame->GetRectRelativeToSelf();
+  } else {
+    rect = nsRect(nsPresContext::CSSPixelsToAppUnits(x),
+                  nsPresContext::CSSPixelsToAppUnits(y),
+                  nsPresContext::CSSPixelsToAppUnits(w),
+                  nsPresContext::CSSPixelsToAppUnits(h));
+  }
+  presShell->ScrollFrameIntoView(
+      primaryFrame, Some(rect),
+      ScrollAxis(WhereToScroll::Center, WhenToScroll::IfNotFullyVisible),
+      ScrollAxis(WhereToScroll::Center, WhenToScroll::IfNotFullyVisible),
+      ScrollFlags::ScrollOverflowHidden);
+  // If a _visual_ scroll update is pending, cancel it; otherwise, it will
+  // clobber next scroll (e.g. subsequent window.scrollTo(0, 0) wlll break).
+  if (presShell->GetPendingVisualScrollUpdate()) {
+    presShell->AcknowledgePendingVisualScrollUpdate();
+    presShell->ClearPendingVisualScrollUpdate();
+  }
+}
+
 already_AddRefed<DOMQuad> nsINode::ConvertQuadFromNode(
     DOMQuad& aQuad, const GeometryNode& aFrom,
     const ConvertCoordinateOptions& aOptions, CallerType aCallerType,
diff --git a/dom/base/nsINode.h b/dom/base/nsINode.h
index c7d56c4f8ed4400ac7e5dd5b168862c8bfc8c7aa..1a8469bb00cfdcc1b6e7675c4a19e4ae9ad18637 100644
--- a/dom/base/nsINode.h
+++ b/dom/base/nsINode.h
@@ -2322,6 +2322,10 @@ class nsINode : public mozilla::dom::EventTarget {
                                    nsTArray<RefPtr<DOMQuad>>& aResult,
                                    ErrorResult& aRv);
 
+  void ScrollRectIntoViewIfNeeded(int32_t x, int32_t y,
+                                  int32_t w, int32_t h,
+                                  ErrorResult& aRv);
+
   already_AddRefed<DOMQuad> ConvertQuadFromNode(
       DOMQuad& aQuad, const TextOrElementOrDocument& aFrom,
       const ConvertCoordinateOptions& aOptions, CallerType aCallerType,
diff --git a/dom/base/nsJSUtils.cpp b/dom/base/nsJSUtils.cpp
index 48df3ae2d30b975269d06e6354b143abd3e5fcd8..87c8d237355668b0ff324f49be879219b1761083 100644
--- a/dom/base/nsJSUtils.cpp
+++ b/dom/base/nsJSUtils.cpp
@@ -149,6 +149,11 @@ bool nsJSUtils::GetScopeChainForElement(
   return true;
 }
 
+/* static */
+bool nsJSUtils::SetTimeZoneOverride(const char* timezoneId) {
+  return JS::SetTimeZoneOverride(timezoneId);
+}
+
 /* static */
 void nsJSUtils::ResetTimeZone() { JS::ResetTimeZone(); }
 
diff --git a/dom/base/nsJSUtils.h b/dom/base/nsJSUtils.h
index 8b4c1492c64884d83eb1553bc40b921e0da601b7..ee66eaa21d8e8c208204ef73fca5b3d78abefb24 100644
--- a/dom/base/nsJSUtils.h
+++ b/dom/base/nsJSUtils.h
@@ -71,6 +71,7 @@ class nsJSUtils {
       JSContext* aCx, mozilla::dom::Element* aElement,
       JS::MutableHandleVector<JSObject*> aScopeChain);
 
+  static bool SetTimeZoneOverride(const char* timezoneId);
   static void ResetTimeZone();
 
   static bool DumpEnabled();
diff --git a/dom/chrome-webidl/BrowsingContext.webidl b/dom/chrome-webidl/BrowsingContext.webidl
index 28e8d8cb9c61ff8362b2d191d47c3630d2cb0b34..0058e60aaab21f8003bbe1bf3f271c63ed78f29a 100644
--- a/dom/chrome-webidl/BrowsingContext.webidl
+++ b/dom/chrome-webidl/BrowsingContext.webidl
@@ -61,6 +61,15 @@ enum ForcedColorsOverride {
   "active",
 };
 
+/**
+ * CSS prefers-reduced-motion values.
+ */
+enum PrefersReducedMotionOverride {
+  "none",
+  "reduce",
+  "no-preference",
+};
+
 /**
  * Allowed overrides of platform/pref default behaviour for touch events.
  */
@@ -220,6 +229,9 @@ interface BrowsingContext {
   // Forced-colors simulation, for DevTools
   [SetterThrows] attribute ForcedColorsOverride forcedColorsOverride;
 
+  // Reduced-Motion simulation, for DevTools.
+  [SetterThrows] attribute PrefersReducedMotionOverride prefersReducedMotionOverride;
+
   /**
    * A unique identifier for the browser element that is hosting this
    * BrowsingContext tree. Every BrowsingContext in the element's tree will
diff --git a/dom/geolocation/Geolocation.cpp b/dom/geolocation/Geolocation.cpp
index 140ad5a3e651cc3dc7c31ff7efebbd3cecb0076d..cae2d2af93a3d881d2a934d446945f356c3b6070 100644
--- a/dom/geolocation/Geolocation.cpp
+++ b/dom/geolocation/Geolocation.cpp
@@ -29,6 +29,7 @@
 #include "nsComponentManagerUtils.h"
 #include "nsContentPermissionHelper.h"
 #include "nsContentUtils.h"
+#include "nsDocShell.h"
 #include "nsGlobalWindowInner.h"
 #include "mozilla/dom/Document.h"
 #include "nsINamed.h"
@@ -432,10 +433,8 @@ nsGeolocationRequest::Allow(JS::Handle<JS::Value> aChoices) {
     return NS_OK;
   }
 
-  RefPtr<nsGeolocationService> gs =
-      nsGeolocationService::GetGeolocationService();
-
-  bool canUseCache = false;
+  nsGeolocationService* gs = mLocator->GetGeolocationService();
+  bool canUseCache = gs != nsGeolocationService::sService.get();
   CachedPositionAndAccuracy lastPosition = gs->GetCachedPosition();
   if (lastPosition.position) {
     EpochTimeStamp cachedPositionTime_ms;
@@ -643,8 +642,7 @@ void nsGeolocationRequest::Shutdown() {
   // If there are no other high accuracy requests, the geolocation service will
   // notify the provider to switch to the default accuracy.
   if (mOptions && mOptions->mEnableHighAccuracy) {
-    RefPtr<nsGeolocationService> gs =
-        nsGeolocationService::GetGeolocationService();
+    nsGeolocationService* gs = mLocator ? mLocator->GetGeolocationService() : nullptr;
     if (gs) {
       gs->UpdateAccuracy();
     }
@@ -961,8 +959,14 @@ void nsGeolocationService::StopDevice() {
 StaticRefPtr<nsGeolocationService> nsGeolocationService::sService;
 
 already_AddRefed<nsGeolocationService>
-nsGeolocationService::GetGeolocationService() {
+nsGeolocationService::GetGeolocationService(nsDocShell* docShell) {
   RefPtr<nsGeolocationService> result;
+  if (docShell) {
+    result = docShell->GetGeolocationServiceOverride();
+    if (result)
+      return result.forget();
+  }
+
   if (nsGeolocationService::sService) {
     result = nsGeolocationService::sService;
 
@@ -1054,7 +1058,9 @@ nsresult Geolocation::Init(nsPIDOMWindowInner* aContentDom) {
   // If no aContentDom was passed into us, we are being used
   // by chrome/c++ and have no mOwner, no mPrincipal, and no need
   // to prompt.
-  mService = nsGeolocationService::GetGeolocationService();
+  nsCOMPtr<Document> doc = aContentDom ? aContentDom->GetDoc() : nullptr;
+  mService = nsGeolocationService::GetGeolocationService(
+      doc ? static_cast<nsDocShell*>(doc->GetDocShell()) : nullptr);
   if (mService) {
     mService->AddLocator(this);
   }
diff --git a/dom/geolocation/Geolocation.h b/dom/geolocation/Geolocation.h
index 992de29b5d2d09c19e55ebb2502215ec9d05a171..cdc20567b693283b0fd5a5923f7ea54210bd1712 100644
--- a/dom/geolocation/Geolocation.h
+++ b/dom/geolocation/Geolocation.h
@@ -31,6 +31,7 @@
 
 #include "nsIGeolocationProvider.h"
 #include "mozilla/Attributes.h"
+#include "nsDocShell.h"
 
 class nsGeolocationService;
 class nsGeolocationRequest;
@@ -51,13 +52,14 @@ struct CachedPositionAndAccuracy {
   bool isHighAccuracy;
 };
 
+
 /**
  * Singleton that manages the geolocation provider
  */
 class nsGeolocationService final : public nsIGeolocationUpdate,
                                    public nsIObserver {
  public:
-  static already_AddRefed<nsGeolocationService> GetGeolocationService();
+  static already_AddRefed<nsGeolocationService> GetGeolocationService(nsDocShell* docShell = nullptr);
   static mozilla::StaticRefPtr<nsGeolocationService> sService;
 
   NS_DECL_THREADSAFE_ISUPPORTS
@@ -189,6 +191,8 @@ class Geolocation final : public nsIGeolocationUpdate, public nsWrapperCache {
       BrowsingContext* aBrowsingContext,
       geolocation::ParentRequestResolver&& aResolver);
 
+  nsGeolocationService* GetGeolocationService() { return mService; };
+
  private:
   ~Geolocation();
 
diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index d40c2a230c8c86f585935061d05e20b405c906fe..29547e7a0d75fdc8b8b30344db32287424e65fba 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -60,6 +60,7 @@
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/HTMLDataListElement.h"
 #include "mozilla/dom/HTMLOptionElement.h"
+#include "nsDocShell.h"
 #include "nsIFrame.h"
 #include "nsRangeFrame.h"
 #include "nsError.h"
@@ -783,6 +784,13 @@ nsresult HTMLInputElement::InitFilePicker(FilePickerType aType) {
     return NS_ERROR_FAILURE;
   }
 
+  nsCOMPtr<nsPIDOMWindowOuter> win = doc->GetWindow();
+  nsDocShell* docShell = win ? static_cast<nsDocShell*>(win->GetDocShell()) : nullptr;
+  if (docShell && docShell->IsFileInputInterceptionEnabled()) {
+    docShell->FilePickerShown(this);
+    return NS_OK;
+  }
+
   if (IsPickerBlocked(doc)) {
     return NS_OK;
   }
diff --git a/dom/interfaces/base/nsIDOMWindowUtils.idl b/dom/interfaces/base/nsIDOMWindowUtils.idl
index 4f0fc82a36c5ef5daa99d3623d4e7dac467038e2..9076e43644a2bd82fbaca41fb0e3559dc5f20c24 100644
--- a/dom/interfaces/base/nsIDOMWindowUtils.idl
+++ b/dom/interfaces/base/nsIDOMWindowUtils.idl
@@ -374,6 +374,26 @@ interface nsIDOMWindowUtils : nsISupports {
                          [optional] in long aButtons,
                          [optional] in unsigned long aIdentifier);
 
+  /**
+   * Playwright: a separate method to dispatch mouse event with a
+   * specific `jugglerEventId`.
+   */
+  [can_run_script]
+  unsigned long jugglerSendMouseEvent(in AString aType,
+                         in float aX,
+                         in float aY,
+                         in long aButton,
+                         in long aClickCount,
+                         in long aModifiers,
+                         in boolean aIgnoreRootScrollFrame,
+                         in float aPressure,
+                         in unsigned short aInputSourceArg,
+                         in boolean aIsDOMEventSynthesized,
+                         in boolean aIsWidgetEventSynthesized,
+                         in long aButtons,
+                         in unsigned long aIdentifier,
+                         in boolean aDisablePointerEvent);
+
   /** Synthesize a touch event. The event types supported are:
    *    touchstart, touchend, touchmove, and touchcancel
    *
diff --git a/dom/ipc/BrowserChild.cpp b/dom/ipc/BrowserChild.cpp
index 017d579a4c529587ff6730a8bbcd748840ff91ac..4be9d8ee6b6c9e4bbc9c7a2568e883ae43039348 100644
--- a/dom/ipc/BrowserChild.cpp
+++ b/dom/ipc/BrowserChild.cpp
@@ -1674,6 +1674,21 @@ void BrowserChild::HandleRealMouseButtonEvent(const WidgetMouseEvent& aEvent,
   if (postLayerization) {
     postLayerization->Register();
   }
+
+  // Playwright: notify content that mouse event has been received and handled.
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (observerService && aEvent.mJugglerEventId) {
+    if (aEvent.mMessage == eMouseUp) {
+      observerService->NotifyObservers(nullptr, "juggler-mouse-event-hit-renderer", NS_ConvertASCIItoUTF16(nsPrintfCString("mouseup %" PRIu32, aEvent.mJugglerEventId)).get());
+    } else if (aEvent.mMessage == eMouseDown) {
+      observerService->NotifyObservers(nullptr, "juggler-mouse-event-hit-renderer", NS_ConvertASCIItoUTF16(nsPrintfCString("mousedown %" PRIu32, aEvent.mJugglerEventId)).get());
+    } else if (aEvent.mMessage == eMouseMove) {
+      observerService->NotifyObservers(nullptr, "juggler-mouse-event-hit-renderer", NS_ConvertASCIItoUTF16(nsPrintfCString("mousemove %" PRIu32, aEvent.mJugglerEventId)).get());
+    } else if (aEvent.mMessage == eContextMenu) {
+      observerService->NotifyObservers(nullptr, "juggler-mouse-event-hit-renderer", NS_ConvertASCIItoUTF16(nsPrintfCString("contextmenu %" PRIu32, aEvent.mJugglerEventId)).get());
+    }
+  }
 }
 
 mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealMouseButtonEvent(
diff --git a/dom/ipc/CoalescedMouseData.cpp b/dom/ipc/CoalescedMouseData.cpp
index 5aa445d2e0a6169e57c44569974d557b3baf7064..671f71979b407f0ca17c66f13805e851ba30479e 100644
--- a/dom/ipc/CoalescedMouseData.cpp
+++ b/dom/ipc/CoalescedMouseData.cpp
@@ -67,6 +67,9 @@ bool CoalescedMouseData::CanCoalesce(const WidgetMouseEvent& aEvent,
           mCoalescedInputEvent->pointerId == aEvent.pointerId &&
           mCoalescedInputEvent->mButton == aEvent.mButton &&
           mCoalescedInputEvent->mButtons == aEvent.mButtons && mGuid == aGuid &&
+          // `mJugglerEventId` is 0 for non-juggler events and a unique number for
+          // juggler-emitted events.
+          mCoalescedInputEvent->mJugglerEventId == aEvent.mJugglerEventId &&
           mInputBlockId == aInputBlockId);
 }
 
diff --git a/dom/media/systemservices/video_engine/desktop_capture_impl.cc b/dom/media/systemservices/video_engine/desktop_capture_impl.cc
index c43a1b3b245101c974742c5e50f54857e538bbfb..c07a568da3342cbf2af07471fa6959cb242b9a4e 100644
--- a/dom/media/systemservices/video_engine/desktop_capture_impl.cc
+++ b/dom/media/systemservices/video_engine/desktop_capture_impl.cc
@@ -52,9 +52,10 @@ namespace webrtc {
 
 DesktopCaptureImpl* DesktopCaptureImpl::Create(const int32_t aModuleId,
                                                const char* aUniqueId,
-                                               const CaptureDeviceType aType) {
+                                               const CaptureDeviceType aType,
+                                               bool aCaptureCursor) {
   return new rtc::RefCountedObject<DesktopCaptureImpl>(aModuleId, aUniqueId,
-                                                       aType);
+                                                       aType, aCaptureCursor);
 }
 
 static DesktopCaptureOptions CreateDesktopCaptureOptions() {
@@ -155,8 +156,10 @@ static std::unique_ptr<DesktopCapturer> CreateTabCapturer(
 
 static std::unique_ptr<DesktopCapturer> CreateDesktopCapturerAndThread(
     CaptureDeviceType aDeviceType, DesktopCapturer::SourceId aSourceId,
-    nsIThread** aOutThread) {
+    nsIThread** aOutThread, bool aCaptureCursor) {
   DesktopCaptureOptions options = CreateDesktopCaptureOptions();
+  if (aCaptureCursor)
+    options.set_prefer_cursor_embedded(aCaptureCursor);
   auto ensureThread = [&]() {
     if (*aOutThread) {
       return *aOutThread;
@@ -253,7 +256,8 @@ static std::unique_ptr<DesktopCapturer> CreateDesktopCapturerAndThread(
 }
 
 DesktopCaptureImpl::DesktopCaptureImpl(const int32_t aId, const char* aUniqueId,
-                                       const CaptureDeviceType aType)
+                                       const CaptureDeviceType aType,
+                                       bool aCaptureCursor)
     : mModuleId(aId),
       mTrackingId(mozilla::TrackingId(CaptureEngineToTrackingSourceStr([&] {
                                         switch (aType) {
@@ -270,6 +274,7 @@ DesktopCaptureImpl::DesktopCaptureImpl(const int32_t aId, const char* aUniqueId,
                                       aId)),
       mDeviceUniqueId(aUniqueId),
       mDeviceType(aType),
+      capture_cursor_(aCaptureCursor),
       mControlThread(mozilla::GetCurrentSerialEventTarget()),
       mNextFrameMinimumTime(Timestamp::Zero()),
       mCallbacks("DesktopCaptureImpl::mCallbacks") {}
@@ -294,6 +299,19 @@ void DesktopCaptureImpl::DeRegisterCaptureDataCallback(
   }
 }
 
+void DesktopCaptureImpl::RegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) {
+  rtc::CritScope lock(&mApiCs);
+  _rawFrameCallbacks.insert(rawFrameCallback);
+}
+
+void DesktopCaptureImpl::DeRegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) {
+  rtc::CritScope lock(&mApiCs);
+  auto it = _rawFrameCallbacks.find(rawFrameCallback);
+  if (it != _rawFrameCallbacks.end()) {
+    _rawFrameCallbacks.erase(it);
+  }
+}
+
 int32_t DesktopCaptureImpl::StopCaptureIfAllClientsClose() {
   {
     auto callbacks = mCallbacks.Lock();
@@ -333,7 +351,7 @@ int32_t DesktopCaptureImpl::StartCapture(
 
   DesktopCapturer::SourceId sourceId = std::stoi(mDeviceUniqueId);
   std::unique_ptr capturer = CreateDesktopCapturerAndThread(
-      mDeviceType, sourceId, getter_AddRefs(mCaptureThread));
+      mDeviceType, sourceId, getter_AddRefs(mCaptureThread), capture_cursor_);
 
   MOZ_ASSERT(!capturer == !mCaptureThread);
   if (!capturer) {
@@ -441,6 +459,15 @@ void DesktopCaptureImpl::OnCaptureResult(DesktopCapturer::Result aResult,
   frameInfo.height = aFrame->size().height();
   frameInfo.videoType = VideoType::kARGB;
 
+  size_t videoFrameStride =
+      frameInfo.width * DesktopFrame::kBytesPerPixel;
+  {
+    rtc::CritScope cs(&mApiCs);
+    for (auto rawFrameCallback : _rawFrameCallbacks) {
+      rawFrameCallback->OnRawFrame(videoFrame, videoFrameStride, frameInfo);
+    }
+  }
+
   size_t videoFrameLength =
       frameInfo.width * frameInfo.height * DesktopFrame::kBytesPerPixel;
 
diff --git a/dom/media/systemservices/video_engine/desktop_capture_impl.h b/dom/media/systemservices/video_engine/desktop_capture_impl.h
index a76b7de569db1cb42728a5514fb80e5c46e0344e..3d61ad8d3aa4a7eaf96957dcd680e1e1ee8abdf4 100644
--- a/dom/media/systemservices/video_engine/desktop_capture_impl.h
+++ b/dom/media/systemservices/video_engine/desktop_capture_impl.h
@@ -26,6 +26,7 @@
 #include "api/video/video_sink_interface.h"
 #include "modules/desktop_capture/desktop_capturer.h"
 #include "modules/video_capture/video_capture.h"
+#include "rtc_base/deprecated/recursive_critical_section.h"
 #include "mozilla/DataMutex.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/TimeStamp.h"
@@ -42,17 +43,44 @@ namespace webrtc {
 
 class VideoCaptureEncodeInterface;
 
+class RawFrameCallback {
+ public:
+  virtual ~RawFrameCallback() {}
+
+  virtual void OnRawFrame(uint8_t* videoFrame, size_t videoFrameLength, const VideoCaptureCapability& frameInfo) = 0;
+};
+
+class VideoCaptureModuleEx : public VideoCaptureModule {
+ public:
+  virtual ~VideoCaptureModuleEx() {}
+
+  virtual void RegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) = 0;
+  virtual void DeRegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) = 0;
+  int32_t StartCaptureCounted(const VideoCaptureCapability& aCapability) {
+    ++capture_counter_;
+    return capture_counter_ == 1 ? StartCapture(aCapability) : 0;
+  }
+
+  int32_t StopCaptureCounted() {
+    --capture_counter_;
+    return capture_counter_ == 0 ? StopCapture() : 0;
+  }
+
+ private:
+  int32_t capture_counter_ = 0;
+};
+
 // Reuses the video engine pipeline for screen sharing.
 // As with video, DesktopCaptureImpl is a proxy for screen sharing
 // and follows the video pipeline design
 class DesktopCaptureImpl : public DesktopCapturer::Callback,
-                           public VideoCaptureModule {
+                           public VideoCaptureModuleEx {
  public:
   /* Create a screen capture modules object
    */
   static DesktopCaptureImpl* Create(
       const int32_t aModuleId, const char* aUniqueId,
-      const mozilla::camera::CaptureDeviceType aType);
+      const mozilla::camera::CaptureDeviceType aType, bool aCaptureCursor = true);
 
   [[nodiscard]] static std::shared_ptr<VideoCaptureModule::DeviceInfo>
   CreateDeviceInfo(const int32_t aId,
@@ -66,6 +94,8 @@ class DesktopCaptureImpl : public DesktopCapturer::Callback,
   void DeRegisterCaptureDataCallback(
       rtc::VideoSinkInterface<VideoFrame>* aCallback) override;
   int32_t StopCaptureIfAllClientsClose() override;
+  void RegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) override;
+  void DeRegisterRawFrameCallback(RawFrameCallback* rawFrameCallback) override;
 
   int32_t SetCaptureRotation(VideoRotation aRotation) override;
   bool SetApplyRotation(bool aEnable) override;
@@ -89,7 +119,8 @@ class DesktopCaptureImpl : public DesktopCapturer::Callback,
 
  protected:
   DesktopCaptureImpl(const int32_t aId, const char* aUniqueId,
-                     const mozilla::camera::CaptureDeviceType aType);
+                     const mozilla::camera::CaptureDeviceType aType,
+                     bool aCaptureCusor);
   virtual ~DesktopCaptureImpl();
 
  private:
@@ -98,6 +129,9 @@ class DesktopCaptureImpl : public DesktopCapturer::Callback,
   void InitOnThread(std::unique_ptr<DesktopCapturer> aCapturer, int aFramerate);
   void UpdateOnThread(int aFramerate);
   void ShutdownOnThread();
+
+  rtc::RecursiveCriticalSection mApiCs;
+  std::set<RawFrameCallback*> _rawFrameCallbacks;
   // DesktopCapturer::Callback interface.
   void OnCaptureResult(DesktopCapturer::Result aResult,
                        std::unique_ptr<DesktopFrame> aFrame) override;
@@ -105,6 +139,8 @@ class DesktopCaptureImpl : public DesktopCapturer::Callback,
   // Notifies all mCallbacks of OnFrame(). mCaptureThread only.
   void NotifyOnFrame(const VideoFrame& aFrame);
 
+  bool capture_cursor_ = true;
+
   // Control thread on which the public API is called.
   const nsCOMPtr<nsISerialEventTarget> mControlThread;
   // Set in StartCapture.
diff --git a/dom/script/ScriptSettings.cpp b/dom/script/ScriptSettings.cpp
index 3b39538e51840cd9b1685b2efd2ff2e9ec83608a..c7bf4f2d53b58bbacb22b3ebebf6f3fc9b5e445f 100644
--- a/dom/script/ScriptSettings.cpp
+++ b/dom/script/ScriptSettings.cpp
@@ -150,6 +150,30 @@ ScriptSettingsStackEntry::~ScriptSettingsStackEntry() {
   MOZ_ASSERT_IF(mGlobalObject, mGlobalObject->HasJSGlobal());
 }
 
+static nsIGlobalObject* UnwrapSandboxGlobal(nsIGlobalObject* global) {
+  if (!global)
+    return global;
+  JSObject* globalObject = global->GetGlobalJSObject();
+  if (!globalObject)
+    return global;
+  JSContext* cx = nsContentUtils::GetCurrentJSContext();
+  if (!cx)
+    return global;
+  JS::Rooted<JSObject*> proto(cx);
+  JS::RootedObject rootedGlobal(cx, globalObject);
+  if (!JS_GetPrototype(cx, rootedGlobal, &proto))
+    return global;
+  if (!proto || !xpc::IsSandboxPrototypeProxy(proto))
+    return global;
+  // If this is a sandbox associated with a DOMWindow via a
+  // sandboxPrototype, use that DOMWindow. This supports GreaseMonkey
+  // and JetPack content scripts.
+  proto = js::CheckedUnwrapDynamic(proto, cx, /* stopAtWindowProxy = */ false);
+  if (!proto)
+    return global;
+  return xpc::WindowGlobalOrNull(proto);
+}
+
 // If the entry or incumbent global ends up being something that the subject
 // principal doesn't subsume, we don't want to use it. This never happens on
 // the web, but can happen with asymmetric privilege relationships (i.e.
@@ -177,7 +201,7 @@ static nsIGlobalObject* ClampToSubject(nsIGlobalObject* aGlobalOrNull) {
   NS_ENSURE_TRUE(globalPrin, GetCurrentGlobal());
   if (!nsContentUtils::SubjectPrincipalOrSystemIfNativeCaller()
            ->SubsumesConsideringDomain(globalPrin)) {
-    return GetCurrentGlobal();
+    return UnwrapSandboxGlobal(GetCurrentGlobal());
   }
 
   return aGlobalOrNull;
diff --git a/dom/security/nsCSPUtils.cpp b/dom/security/nsCSPUtils.cpp
index 17a205b2607208a696a470f81223c4d2618e6bec..90dc5c04f395a3e7c98cc6eff146aa78dc03d1cf 100644
--- a/dom/security/nsCSPUtils.cpp
+++ b/dom/security/nsCSPUtils.cpp
@@ -23,6 +23,7 @@
 #include "nsSandboxFlags.h"
 #include "nsServiceManagerUtils.h"
 #include "nsWhitespaceTokenizer.h"
+#include "nsDocShell.h"
 
 #include "mozilla/Assertions.h"
 #include "mozilla/Components.h"
@@ -134,6 +135,11 @@ void CSP_ApplyMetaCSPToDoc(mozilla::dom::Document& aDoc,
     return;
   }
 
+  if (aDoc.GetDocShell() &&
+      nsDocShell::Cast(aDoc.GetDocShell())->IsBypassCSPEnabled()) {
+    return;
+  }
+
   nsAutoString policyStr(
       nsContentUtils::TrimWhitespace<nsContentUtils::IsHTMLWhitespace>(
           aPolicyStr));
diff --git a/dom/webidl/GeometryUtils.webidl b/dom/webidl/GeometryUtils.webidl
index 2f71b284ee5f7e11f117c447834b48355784448c..2640bd57123c2b03bf4b06a2419cd020ba95f155 100644
--- a/dom/webidl/GeometryUtils.webidl
+++ b/dom/webidl/GeometryUtils.webidl
@@ -16,6 +16,8 @@ dictionary BoxQuadOptions {
   GeometryNode relativeTo;
   [ChromeOnly]
   boolean createFramesForSuppressedWhitespace = true;
+  [ChromeOnly]
+  boolean recurseWhenNoFrame = false;
 };
 
 dictionary ConvertCoordinateOptions {
@@ -27,6 +29,9 @@ interface mixin GeometryUtils {
   [Throws, Func="nsINode::HasBoxQuadsSupport", NeedsCallerType]
   sequence<DOMQuad> getBoxQuads(optional BoxQuadOptions options = {});
 
+  [ChromeOnly, Throws, Func="nsINode::HasBoxQuadsSupport"]
+  undefined scrollRectIntoViewIfNeeded(long x, long y, long w, long h);
+
   /* getBoxQuadsFromWindowOrigin is similar to getBoxQuads, but the
    * returned quads are further translated relative to the window
    * origin -- which is not the layout origin. Further translation
diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
index be23f9f192208c30849ff640ab67debdef3f3ca6..6c14aa9dd751f20838c915b5a0a3d66f13f9dcc5 100644
--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -1005,7 +1005,7 @@ void PrefLanguagesChanged(const char* /* aPrefName */, void* /* aClosure */) {
   AssertIsOnMainThread();
 
   nsTArray<nsString> languages;
-  Navigator::GetAcceptLanguages(languages);
+  Navigator::GetAcceptLanguages(nullptr, languages);
 
   RuntimeService* runtime = RuntimeService::GetService();
   if (runtime) {
@@ -1191,8 +1191,7 @@ bool RuntimeService::RegisterWorker(WorkerPrivate& aWorkerPrivate) {
       }
 
       // The navigator overridden properties should have already been read.
-
-      Navigator::GetAcceptLanguages(mNavigatorProperties.mLanguages);
+      Navigator::GetAcceptLanguages(nullptr, mNavigatorProperties.mLanguages);
       mNavigatorPropertiesLoaded = true;
     }
 
@@ -1813,6 +1812,13 @@ void RuntimeService::PropagateStorageAccessPermissionGranted(
   }
 }
 
+void RuntimeService::ResetDefaultLocaleInAllWorkers() {
+  AssertIsOnMainThread();
+  BroadcastAllWorkers([](auto& worker) {
+    worker.ResetDefaultLocale();
+  });
+}
+
 template <typename Func>
 void RuntimeService::BroadcastAllWorkers(const Func& aFunc) {
   AssertIsOnMainThread();
@@ -2338,6 +2344,14 @@ void PropagateStorageAccessPermissionGrantedToWorkers(
   }
 }
 
+void ResetDefaultLocaleInAllWorkers() {
+  AssertIsOnMainThread();
+  RuntimeService* runtime = RuntimeService::GetService();
+  if (runtime) {
+    runtime->ResetDefaultLocaleInAllWorkers();
+  }
+}
+
 WorkerPrivate* GetWorkerPrivateFromContext(JSContext* aCx) {
   MOZ_ASSERT(!NS_IsMainThread());
   MOZ_ASSERT(aCx);
diff --git a/dom/workers/RuntimeService.h b/dom/workers/RuntimeService.h
index 534bbe9ec4f0261189eb3322c1229c1eb5d8802e..6aa99b64fdbbff3704602e944b129879fbdf8c15 100644
--- a/dom/workers/RuntimeService.h
+++ b/dom/workers/RuntimeService.h
@@ -112,6 +112,8 @@ class RuntimeService final : public nsIObserver {
   void PropagateStorageAccessPermissionGranted(
       const nsPIDOMWindowInner& aWindow);
 
+  void ResetDefaultLocaleInAllWorkers();
+
   const NavigatorProperties& GetNavigatorProperties() const {
     return mNavigatorProperties;
   }
diff --git a/dom/workers/WorkerCommon.h b/dom/workers/WorkerCommon.h
index 58894a8361c7ef1dddd481ca5877a209a8b8ff5c..c481d40d79b6397b7f1d571bd9f6ae5c0a946217 100644
--- a/dom/workers/WorkerCommon.h
+++ b/dom/workers/WorkerCommon.h
@@ -47,6 +47,8 @@ void ResumeWorkersForWindow(const nsPIDOMWindowInner& aWindow);
 void PropagateStorageAccessPermissionGrantedToWorkers(
     const nsPIDOMWindowInner& aWindow);
 
+void ResetDefaultLocaleInAllWorkers();
+
 // All of these are implemented in WorkerScope.cpp
 
 bool IsWorkerGlobal(JSObject* global);
diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index ee89a9ffbe33754bd41643555a621ca6f62e5465..9d9ec1aac7858129ad5adef62ab359d1ea667082 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -718,6 +718,18 @@ class UpdateContextOptionsRunnable final : public WorkerControlRunnable {
   }
 };
 
+class ResetDefaultLocaleRunnable final : public WorkerControlRunnable {
+ public:
+  explicit ResetDefaultLocaleRunnable(WorkerPrivate* aWorkerPrivate)
+      : WorkerControlRunnable("ResetDefaultLocaleRunnable") {}
+
+  virtual bool WorkerRun(JSContext* aCx,
+                         WorkerPrivate* aWorkerPrivate) override {
+    aWorkerPrivate->ResetDefaultLocaleInternal(aCx);
+    return true;
+  }
+};
+
 class UpdateLanguagesRunnable final : public WorkerThreadRunnable {
   nsTArray<nsString> mLanguages;
 
@@ -2131,6 +2143,16 @@ void WorkerPrivate::UpdateContextOptions(
   }
 }
 
+void WorkerPrivate::ResetDefaultLocale() {
+  AssertIsOnParentThread();
+
+  RefPtr<ResetDefaultLocaleRunnable> runnable =
+      new ResetDefaultLocaleRunnable(this);
+  if (!runnable->Dispatch(this)) {
+    NS_WARNING("Failed to reset default locale in worker!");
+  }
+}
+
 void WorkerPrivate::UpdateLanguages(const nsTArray<nsString>& aLanguages) {
   AssertIsOnParentThread();
 
@@ -5768,6 +5790,15 @@ void WorkerPrivate::UpdateContextOptionsInternal(
   }
 }
 
+void WorkerPrivate::ResetDefaultLocaleInternal(JSContext* aCx) {
+  JS_ResetDefaultLocale(JS_GetRuntime(aCx));
+  auto data = mWorkerThreadAccessible.Access();
+
+  for (uint32_t index = 0; index < data->mChildWorkers.Length(); index++) {
+    data->mChildWorkers[index]->ResetDefaultLocale();
+  }
+}
+
 void WorkerPrivate::UpdateLanguagesInternal(
     const nsTArray<nsString>& aLanguages) {
   WorkerGlobalScope* globalScope = GlobalScope();
diff --git a/dom/workers/WorkerPrivate.h b/dom/workers/WorkerPrivate.h
index 8ca40304e014da2e6898f71ac214f7ca1ab19e87..e0179f6db7fdc679f104bf180c181ab1ac85b4ad 100644
--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -433,6 +433,8 @@ class WorkerPrivate final
   void UpdateContextOptionsInternal(JSContext* aCx,
                                     const JS::ContextOptions& aContextOptions);
 
+  void ResetDefaultLocaleInternal(JSContext* aCx);
+
   void UpdateLanguagesInternal(const nsTArray<nsString>& aLanguages);
 
   void UpdateJSWorkerMemoryParameterInternal(JSContext* aCx, JSGCParamKey key,
@@ -1070,6 +1072,8 @@ class WorkerPrivate final
 
   void UpdateContextOptions(const JS::ContextOptions& aContextOptions);
 
+  void ResetDefaultLocale();
+
   void UpdateLanguages(const nsTArray<nsString>& aLanguages);
 
   void UpdateJSWorkerMemoryParameter(JSGCParamKey key, Maybe<uint32_t> value);
diff --git a/intl/components/src/TimeZone.cpp b/intl/components/src/TimeZone.cpp
index 7a069ef0c59895cf1f8dc35d612f1494c9c9f1ef..5b09dfdcc5323def65c35b0696141b44eef9dcda 100644
--- a/intl/components/src/TimeZone.cpp
+++ b/intl/components/src/TimeZone.cpp
@@ -16,6 +16,7 @@
 
 namespace mozilla::intl {
 
+
 /* static */
 Result<UniquePtr<TimeZone>, ICUError> TimeZone::TryCreate(
     Maybe<Span<const char16_t>> aTimeZoneOverride) {
@@ -318,6 +319,13 @@ static ICUResult SetDefaultTimeZone(TimeZoneIdentifierVector& timeZone) {
 }
 #endif
 
+bool TimeZone::IsValidTimeZoneId(const char* timeZoneId) {
+  // Validate timezone id.
+  mozilla::UniquePtr<icu::TimeZone> timeZone(icu::TimeZone::createTimeZone(
+      icu::UnicodeString(timeZoneId, -1, US_INV)));
+  return timeZone && *timeZone != icu::TimeZone::getUnknown();
+}
+
 Result<bool, ICUError> TimeZone::SetDefaultTimeZone(
     Span<const char> aTimeZone) {
 #if MOZ_INTL_USE_ICU_CPP_TIMEZONE
diff --git a/intl/components/src/TimeZone.h b/intl/components/src/TimeZone.h
index 89770839ae108b5f3462a7f20684fdb72c4ab2fb..a7e40d6b7c33c234b41e586eac573ba4ce3a7d18 100644
--- a/intl/components/src/TimeZone.h
+++ b/intl/components/src/TimeZone.h
@@ -191,6 +191,8 @@ class TimeZone final {
     return FillBufferWithICUCall(aBuffer, ucal_getHostTimeZone);
   }
 
+  static bool IsValidTimeZoneId(const char* timeZoneId);
+
   /**
    * Set the default time zone.
    */
diff --git a/js/public/Date.h b/js/public/Date.h
index 523e84c8c93f4221701f90f2e8ee146ec8e1adbd..98d5b1176e5378431b859a2dbd4d4e778d236e78 100644
--- a/js/public/Date.h
+++ b/js/public/Date.h
@@ -55,6 +55,8 @@ namespace JS {
  */
 extern JS_PUBLIC_API void ResetTimeZone();
 
+extern JS_PUBLIC_API bool SetTimeZoneOverride(const char* timezoneId);
+
 class ClippedTime;
 inline ClippedTime TimeClip(double time);
 
diff --git a/js/src/debugger/Object.cpp b/js/src/debugger/Object.cpp
index 880e716c24464c93283410417f8e69d6d233d105..6e046fbd2e643dace5ad7796740253df3ddf2cbe 100644
--- a/js/src/debugger/Object.cpp
+++ b/js/src/debugger/Object.cpp
@@ -2474,7 +2474,11 @@ Maybe<Completion> DebuggerObject::call(JSContext* cx,
         invokeArgs[i].set(args2[i]);
       }
 
+      // Disable CSP for the scope of the call.
+      const JSSecurityCallbacks* securityCallbacks = JS_GetSecurityCallbacks(cx);
+      JS_SetSecurityCallbacks(cx, nullptr);
       ok = js::Call(cx, calleev, thisv, invokeArgs, &result);
+      JS_SetSecurityCallbacks(cx, securityCallbacks);
     }
   }
 
diff --git a/js/src/vm/DateTime.cpp b/js/src/vm/DateTime.cpp
index 623a6863a54fb0d653ebe55fd83356f1a8c8be15..1c0ef7b0d3ee2f61de728a68dd704a5d09757b38 100644
--- a/js/src/vm/DateTime.cpp
+++ b/js/src/vm/DateTime.cpp
@@ -186,6 +186,11 @@ void js::DateTimeInfo::internalResetTimeZone(ResetTimeZoneMode mode) {
   }
 }
 
+void js::DateTimeInfo::internalSetTimeZoneOverride(std::string timeZone) {
+  timeZoneOverride_ = std::move(timeZone);
+  internalResetTimeZone(ResetTimeZoneMode::ResetEvenIfOffsetUnchanged);
+}
+
 void js::DateTimeInfo::updateTimeZone() {
   MOZ_ASSERT(timeZoneStatus_ != TimeZoneStatus::Valid);
 
@@ -529,10 +534,24 @@ void js::ResetTimeZoneInternal(ResetTimeZoneMode mode) {
   js::DateTimeInfo::resetTimeZone(mode);
 }
 
+void js::SetTimeZoneOverrideInternal(std::string timeZone) {
+  auto guard = js::DateTimeInfo::instance->lock();
+  guard->internalSetTimeZoneOverride(timeZone);
+}
+
 JS_PUBLIC_API void JS::ResetTimeZone() {
   js::ResetTimeZoneInternal(js::ResetTimeZoneMode::ResetEvenIfOffsetUnchanged);
 }
 
+JS_PUBLIC_API bool JS::SetTimeZoneOverride(const char* timeZoneId) {
+  if (!mozilla::intl::TimeZone::IsValidTimeZoneId(timeZoneId)) {
+    fprintf(stderr, "Invalid timezone id: %s\n", timeZoneId);
+    return false;
+  }
+  js::SetTimeZoneOverrideInternal(std::string(timeZoneId));
+  return true;
+}
+
 #if JS_HAS_INTL_API
 #  if defined(XP_WIN)
 static bool IsOlsonCompatibleWindowsTimeZoneId(std::string_view tz) {
@@ -750,6 +769,15 @@ static bool ReadTimeZoneLink(std::string_view tz,
 
 void js::DateTimeInfo::internalResyncICUDefaultTimeZone() {
 #if JS_HAS_INTL_API
+  if (!timeZoneOverride_.empty()) {
+    mozilla::Span<const char> tzid = mozilla::Span(timeZoneOverride_.data(), timeZoneOverride_.length());
+    auto result = mozilla::intl::TimeZone::SetDefaultTimeZone(tzid);
+    if (result.isErr()) {
+      fprintf(stderr, "ERROR: failed to setup default time zone\n");
+    }
+    return;
+  }
+
   // In the future we should not be setting a default ICU time zone at all,
   // instead all accesses should go through the appropriate DateTimeInfo
   // instance depending on the resist fingerprinting status. For now we return
@@ -761,7 +789,6 @@ void js::DateTimeInfo::internalResyncICUDefaultTimeZone() {
 
   if (const char* tzenv = std::getenv("TZ")) {
     std::string_view tz(tzenv);
-
     mozilla::Span<const char> tzid;
 
 #  if defined(XP_WIN)
diff --git a/js/src/vm/DateTime.h b/js/src/vm/DateTime.h
index fd6d7ae078b8f6b3cc46a4a993a1e044a7128c90..4743094e489122dd9ee8ab9a7a175dd7e928859d 100644
--- a/js/src/vm/DateTime.h
+++ b/js/src/vm/DateTime.h
@@ -65,6 +65,8 @@ enum class ResetTimeZoneMode : bool {
  */
 extern void ResetTimeZoneInternal(ResetTimeZoneMode mode);
 
+extern void SetTimeZoneOverrideInternal(std::string timeZone);
+
 /**
  * Stores date/time information, particularly concerning the current local
  * time zone, and implements a small cache for daylight saving time offset
@@ -225,6 +227,7 @@ class DateTimeInfo {
  private:
   // The method below should only be called via js::ResetTimeZoneInternal().
   friend void js::ResetTimeZoneInternal(ResetTimeZoneMode);
+  friend void js::SetTimeZoneOverrideInternal(std::string);
 
   static void resetTimeZone(ResetTimeZoneMode mode) {
     {
@@ -321,6 +324,8 @@ class DateTimeInfo {
   JS::UniqueChars locale_;
   JS::UniqueTwoByteChars standardName_;
   JS::UniqueTwoByteChars daylightSavingsName_;
+
+  std::string timeZoneOverride_;
 #else
   // Restrict the data-time range to the minimum required time_t range as
   // specified in POSIX. Most operating systems support 64-bit time_t
@@ -336,6 +341,8 @@ class DateTimeInfo {
 
   void internalResetTimeZone(ResetTimeZoneMode mode);
 
+  void internalSetTimeZoneOverride(std::string timeZone);
+
   void updateTimeZone();
 
   void internalResyncICUDefaultTimeZone();
diff --git a/layout/base/GeometryUtils.cpp b/layout/base/GeometryUtils.cpp
index 0ec6ee3eb37c6493d8a25352fd0e54e1927bceab..885dba71bc5815e5f6f3ec2700c376aa119b30d0 100644
--- a/layout/base/GeometryUtils.cpp
+++ b/layout/base/GeometryUtils.cpp
@@ -23,6 +23,7 @@
 #include "nsContentUtils.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsLayoutUtils.h"
+#include "ChildIterator.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -261,11 +262,27 @@ static bool CheckFramesInSameTopLevelBrowsingContext(nsIFrame* aFrame1,
   return false;
 }
 
+static nsIFrame* GetFrameForNode(nsINode* aNode,
+                                 bool aCreateFramesForSuppressedWhitespace,
+                                 bool aRecurseWhenNoFrame) {
+  nsIFrame* frame = GetFrameForNode(aNode, aCreateFramesForSuppressedWhitespace);
+  if (!frame && aRecurseWhenNoFrame && aNode->IsContent()) {
+    dom::FlattenedChildIterator iter(aNode->AsContent());
+    for (nsIContent* child = iter.GetNextChild(); child; child = iter.GetNextChild()) {
+      frame = GetFrameForNode(child, aCreateFramesForSuppressedWhitespace, aRecurseWhenNoFrame);
+      if (frame) {
+        break;
+      }
+    }
+  }
+  return frame;
+}
+
 void GetBoxQuads(nsINode* aNode, const dom::BoxQuadOptions& aOptions,
                  nsTArray<RefPtr<DOMQuad> >& aResult, CallerType aCallerType,
                  ErrorResult& aRv) {
   nsIFrame* frame =
-      GetFrameForNode(aNode, aOptions.mCreateFramesForSuppressedWhitespace);
+      GetFrameForNode(aNode, aOptions.mCreateFramesForSuppressedWhitespace, aOptions.mRecurseWhenNoFrame);
   if (!frame) {
     // No boxes to return
     return;
@@ -280,7 +297,7 @@ void GetBoxQuads(nsINode* aNode, const dom::BoxQuadOptions& aOptions,
   // when that happens and re-check it.
   if (!weakFrame.IsAlive()) {
     frame =
-        GetFrameForNode(aNode, aOptions.mCreateFramesForSuppressedWhitespace);
+        GetFrameForNode(aNode, aOptions.mCreateFramesForSuppressedWhitespace, aOptions.mRecurseWhenNoFrame);
     if (!frame) {
       // No boxes to return
       return;
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index 27fd20e845af4c96cd1798debba57422872fab66..bcd1351884fb6de8f04062283dc677e057ada988 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -11194,7 +11194,9 @@ bool PresShell::ComputeActiveness() const {
     if (!browserChild->IsVisible()) {
       MOZ_LOG(gLog, LogLevel::Debug,
               (" > BrowserChild %p is not visible", browserChild));
-      return false;
+      bool isActive;
+      root->GetDocShell()->GetForceActiveState(&isActive);
+      return isActive;
     }
 
     // If the browser is visible but just due to be preserving layers
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 43d7e5008b352b7deb198ffc81fedf5de3f4b72a..c62d9f87a84c01994ad735146491219ef4f0e42e 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -699,6 +699,10 @@ bool nsLayoutUtils::AllowZoomingForDocument(
       !aDocument->GetPresShell()->AsyncPanZoomEnabled()) {
     return false;
   }
+
+  /* Playwright: disable zooming as we don't support meta viewport tag */
+  if (1 == 1) return false;
+
   // True if we allow zooming for all documents on this platform, or if we are
   // in RDM.
   BrowsingContext* bc = aDocument->GetBrowsingContext();
@@ -9645,6 +9649,9 @@ void nsLayoutUtils::ComputeSystemFont(nsFont* aSystemFont,
 
 /* static */
 bool nsLayoutUtils::ShouldHandleMetaViewport(const Document* aDocument) {
+  /* Playwright: disable meta viewport handling since we don't require one */
+  if (1 == 1) return false;
+
   BrowsingContext* bc = aDocument->GetBrowsingContext();
   return StaticPrefs::dom_meta_viewport_enabled() || (bc && bc->InRDMPane());
 }
diff --git a/layout/style/GeckoBindings.h b/layout/style/GeckoBindings.h
index acb5b24776c8591933d1abcbcc7b254cf2ceb4e4..191ddd1f43bd704294727555c3d5137d69c1460c 100644
--- a/layout/style/GeckoBindings.h
+++ b/layout/style/GeckoBindings.h
@@ -593,6 +593,7 @@ float Gecko_MediaFeatures_GetResolution(const mozilla::dom::Document*);
 bool Gecko_MediaFeatures_PrefersReducedMotion(const mozilla::dom::Document*);
 bool Gecko_MediaFeatures_PrefersReducedTransparency(
     const mozilla::dom::Document*);
+bool Gecko_MediaFeatures_ForcedColors(const mozilla::dom::Document*);
 mozilla::StylePrefersContrast Gecko_MediaFeatures_PrefersContrast(
     const mozilla::dom::Document*);
 mozilla::StylePrefersColorScheme Gecko_MediaFeatures_PrefersColorScheme(
diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
index 94f01a53378c67b78346cf13f43431d9a5d104d9..4861de461648699360ed8c0453126c6c80587745 100644
--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -265,11 +265,7 @@ bool Gecko_MediaFeatures_MatchesPlatform(StylePlatform aPlatform) {
 }
 
 bool Gecko_MediaFeatures_PrefersReducedMotion(const Document* aDocument) {
-  if (aDocument->ShouldResistFingerprinting(
-          RFPTarget::CSSPrefersReducedMotion)) {
-    return false;
-  }
-  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+  return aDocument->PrefersReducedMotion();
 }
 
 bool Gecko_MediaFeatures_PrefersReducedTransparency(const Document* aDocument) {
diff --git a/netwerk/base/LoadInfo.cpp b/netwerk/base/LoadInfo.cpp
index 283e991f921f877ddfc6b15e8dbe08f92bf3342b..7d08aa7fa4a40255a93c617fc2cc99d6b3f666d6 100644
--- a/netwerk/base/LoadInfo.cpp
+++ b/netwerk/base/LoadInfo.cpp
@@ -694,7 +694,8 @@ LoadInfo::LoadInfo(const LoadInfo& rhs)
           rhs.mHasInjectedCookieForCookieBannerHandling),
       mWasSchemelessInput(rhs.mWasSchemelessInput),
       mHttpsUpgradeTelemetry(rhs.mHttpsUpgradeTelemetry),
-      mIsNewWindowTarget(rhs.mIsNewWindowTarget) {
+      mIsNewWindowTarget(rhs.mIsNewWindowTarget),
+      mJugglerLoadIdentifier(rhs.mJugglerLoadIdentifier) {
 }
 
 LoadInfo::LoadInfo(
@@ -2488,4 +2489,16 @@ LoadInfo::SetSkipHTTPSUpgrade(bool aSkipHTTPSUpgrade) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+LoadInfo::GetJugglerLoadIdentifier(uint64_t* aResult) {
+  *aResult = mJugglerLoadIdentifier;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadInfo::SetJugglerLoadIdentifier(uint64_t aID) {
+  mJugglerLoadIdentifier = aID;
+  return NS_OK;
+}
+
 }  // namespace mozilla::net
diff --git a/netwerk/base/LoadInfo.h b/netwerk/base/LoadInfo.h
index 0598c9703fdd0f8f71cc9d88ade4c8bc8b241af6..bfb71b848104c7df0c3784a95801a87d5f9cc20b 100644
--- a/netwerk/base/LoadInfo.h
+++ b/netwerk/base/LoadInfo.h
@@ -413,12 +413,13 @@ class LoadInfo final : public nsILoadInfo {
 
   bool mHasInjectedCookieForCookieBannerHandling = false;
   bool mWasSchemelessInput = false;
-
   nsILoadInfo::HTTPSUpgradeTelemetryType mHttpsUpgradeTelemetry =
       nsILoadInfo::NOT_INITIALIZED;
 
   bool mIsNewWindowTarget = false;
   bool mSkipHTTPSUpgrade = false;
+
+  uint64_t mJugglerLoadIdentifier = 0;
 };
 
 // This is exposed solely for testing purposes and should not be used outside of
diff --git a/netwerk/base/TRRLoadInfo.cpp b/netwerk/base/TRRLoadInfo.cpp
index d1aad5d3a3863f62b17ebb01d9d6dc02c5dbcf71..8b3640504c877fccd75d523dc45c3a1c812f4ceb 100644
--- a/netwerk/base/TRRLoadInfo.cpp
+++ b/netwerk/base/TRRLoadInfo.cpp
@@ -923,5 +923,15 @@ TRRLoadInfo::SetSkipHTTPSUpgrade(bool aSkipHTTPSUpgrade) {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
+NS_IMETHODIMP
+TRRLoadInfo::GetJugglerLoadIdentifier(uint64_t* aResult) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+TRRLoadInfo::SetJugglerLoadIdentifier(uint64_t aResult) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 }  // namespace net
 }  // namespace mozilla
diff --git a/netwerk/base/nsILoadInfo.idl b/netwerk/base/nsILoadInfo.idl
index afe180f91f6b4921408955db499fcb47f1da509f..89e9dd69dccd3bff11076595244e106a06d80de1 100644
--- a/netwerk/base/nsILoadInfo.idl
+++ b/netwerk/base/nsILoadInfo.idl
@@ -1600,4 +1600,6 @@ interface nsILoadInfo : nsISupports
    * When true, this load will never be upgraded to HTTPS.
    */
   [infallible] attribute boolean skipHTTPSUpgrade;
+
+  [infallible] attribute unsigned long long jugglerLoadIdentifier;
 };
diff --git a/netwerk/base/nsINetworkInterceptController.idl b/netwerk/base/nsINetworkInterceptController.idl
index 7f91d2df6f8bb4020c75c132dc8f6bf26625fa1e..ba6569f4be8fc54ec96ee44d5de45a0904c077ba 100644
--- a/netwerk/base/nsINetworkInterceptController.idl
+++ b/netwerk/base/nsINetworkInterceptController.idl
@@ -59,6 +59,7 @@ interface nsIInterceptedChannel : nsISupports
      * results in the resulting client not being controlled.
      */
     void resetInterception(in boolean bypass);
+    void resetInterceptionWithURI(in nsIURI aURI);
 
     /**
      * Set the status and reason for the forthcoming synthesized response.
diff --git a/netwerk/ipc/DocumentLoadListener.cpp b/netwerk/ipc/DocumentLoadListener.cpp
index 82c6137d8c52c8fd2ba3542d6f7a645ad1e73f11..5f31e5e1c9cb44d49ac61b6f6bda0189424c2685 100644
--- a/netwerk/ipc/DocumentLoadListener.cpp
+++ b/netwerk/ipc/DocumentLoadListener.cpp
@@ -172,6 +172,7 @@ static auto CreateDocumentLoadInfo(CanonicalBrowsingContext* aBrowsingContext,
   loadInfo->SetTextDirectiveUserActivation(
       aLoadState->GetTextDirectiveUserActivation());
   loadInfo->SetIsMetaRefresh(aLoadState->IsMetaRefresh());
+  loadInfo->SetJugglerLoadIdentifier(aLoadState->GetLoadIdentifier());
 
   return loadInfo.forget();
 }
diff --git a/netwerk/protocol/http/InterceptedHttpChannel.cpp b/netwerk/protocol/http/InterceptedHttpChannel.cpp
index e81a4538fd45c13aa60d933de5f4f32ce69fb5f2..d7945f81295c497485a09696f06ce041c1cd8079 100644
--- a/netwerk/protocol/http/InterceptedHttpChannel.cpp
+++ b/netwerk/protocol/http/InterceptedHttpChannel.cpp
@@ -727,6 +727,14 @@ NS_IMPL_ISUPPORTS(ResetInterceptionHeaderVisitor, nsIHttpHeaderVisitor)
 
 }  // anonymous namespace
 
+NS_IMETHODIMP
+InterceptedHttpChannel::ResetInterceptionWithURI(nsIURI* aURI) {
+  if (aURI) {
+    mURI = aURI;
+  }
+  return ResetInterception(true);
+}
+
 NS_IMETHODIMP
 InterceptedHttpChannel::ResetInterception(bool aBypass) {
   INTERCEPTED_LOG(("InterceptedHttpChannel::ResetInterception [%p] bypass: %s",
@@ -1140,11 +1148,18 @@ InterceptedHttpChannel::OnStartRequest(nsIRequest* aRequest) {
     GetCallback(mProgressSink);
   }
 
+  // Playwright: main requests in firefox do not have loading principal.
+  // As they are intercepted by Playwright, they don't have
+  // serviceWorkerTainting as well.
+  // Thus these asserts are wrong for Playwright world.
+  // Note: these checks were added in https://github.com/mozilla/gecko-dev/commit/92e2cdde79c11510c3e4192e1b6264d00398ed95
+  /*
   MOZ_ASSERT_IF(!mLoadInfo->GetServiceWorkerTaintingSynthesized(),
                 mLoadInfo->GetLoadingPrincipal());
   // No need to do ORB checks if these conditions hold.
   MOZ_DIAGNOSTIC_ASSERT(mLoadInfo->GetServiceWorkerTaintingSynthesized() ||
                         mLoadInfo->GetLoadingPrincipal()->IsSystemPrincipal());
+  */
 
   if (mPump && mLoadFlags & LOAD_CALL_CONTENT_SNIFFERS) {
     mPump->PeekStream(CallTypeSniffers, static_cast<nsIChannel*>(this));
diff --git a/parser/html/nsHtml5TreeOpExecutor.cpp b/parser/html/nsHtml5TreeOpExecutor.cpp
index d05b06c3f9ddba3b40d5969730474eaf0d843cb1..9b2cc35c504e1044ac681c62c107f8feb6c16938 100644
--- a/parser/html/nsHtml5TreeOpExecutor.cpp
+++ b/parser/html/nsHtml5TreeOpExecutor.cpp
@@ -1334,6 +1334,10 @@ void nsHtml5TreeOpExecutor::UpdateReferrerInfoFromMeta(
 void nsHtml5TreeOpExecutor::AddSpeculationCSP(const nsAString& aCSP) {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
 
+  if (mDocShell && static_cast<nsDocShell*>(mDocShell.get())->IsBypassCSPEnabled()) {
+    return;
+  }
+
   nsresult rv = NS_OK;
   nsCOMPtr<nsIContentSecurityPolicy> preloadCsp = mDocument->GetPreloadCsp();
   if (!preloadCsp) {
diff --git a/security/manager/ssl/nsCertOverrideService.cpp b/security/manager/ssl/nsCertOverrideService.cpp
index b2e328e7c7d7a89be34b84fd176c306a3620c77c..54f24b213bcdc78c702e15d4d45a3943bc082281 100644
--- a/security/manager/ssl/nsCertOverrideService.cpp
+++ b/security/manager/ssl/nsCertOverrideService.cpp
@@ -439,7 +439,12 @@ nsCertOverrideService::HasMatchingOverride(
   bool disableAllSecurityCheck = false;
   {
     MutexAutoLock lock(mMutex);
-    disableAllSecurityCheck = mDisableAllSecurityCheck;
+    if (aOriginAttributes.mUserContextId) {
+      disableAllSecurityCheck = mUserContextIdsWithDisabledSecurityChecks.has(
+          aOriginAttributes.mUserContextId);
+    } else {
+      disableAllSecurityCheck = mDisableAllSecurityCheck;
+    }
   }
   if (disableAllSecurityCheck) {
     *aIsTemporary = false;
@@ -651,14 +656,24 @@ static bool IsDebugger() {
 
 NS_IMETHODIMP
 nsCertOverrideService::
-    SetDisableAllSecurityChecksAndLetAttackersInterceptMyData(bool aDisable) {
-  if (!(PR_GetEnv("XPCSHELL_TEST_PROFILE_DIR") || IsDebugger())) {
+    SetDisableAllSecurityChecksAndLetAttackersInterceptMyData(
+      bool aDisable, uint32_t aUserContextId) {
+  if (false /* juggler hacks */ && !(PR_GetEnv("XPCSHELL_TEST_PROFILE_DIR") || IsDebugger())) {
     return NS_ERROR_NOT_AVAILABLE;
   }
 
   {
     MutexAutoLock lock(mMutex);
-    mDisableAllSecurityCheck = aDisable;
+    if (aUserContextId) {
+      if (aDisable) {
+        mozilla::Unused << mUserContextIdsWithDisabledSecurityChecks.put(aUserContextId);
+      } else {
+        mUserContextIdsWithDisabledSecurityChecks.remove(aUserContextId);
+      }
+      return NS_OK;
+    } else {
+      mDisableAllSecurityCheck = aDisable;
+    }
   }
 
   nsCOMPtr<nsINSSComponent> nss(do_GetService(PSM_COMPONENT_CONTRACTID));
diff --git a/security/manager/ssl/nsCertOverrideService.h b/security/manager/ssl/nsCertOverrideService.h
index 21cff56300db6490cf9649aa62099cb5525749b3..ce9a7fc16c2d5980be166e0f4ab9a25df300ca2f 100644
--- a/security/manager/ssl/nsCertOverrideService.h
+++ b/security/manager/ssl/nsCertOverrideService.h
@@ -118,6 +118,7 @@ class nsCertOverrideService final : public nsICertOverrideService,
 
   mozilla::Mutex mMutex;
   bool mDisableAllSecurityCheck MOZ_GUARDED_BY(mMutex);
+  mozilla::HashSet<uint32_t> mUserContextIdsWithDisabledSecurityChecks MOZ_GUARDED_BY(mMutex);
   nsCOMPtr<nsIFile> mSettingsFile MOZ_GUARDED_BY(mMutex);
   nsTHashtable<nsCertOverrideEntry> mSettingsTable MOZ_GUARDED_BY(mMutex);
 
diff --git a/security/manager/ssl/nsICertOverrideService.idl b/security/manager/ssl/nsICertOverrideService.idl
index 6dfd07d6b676a99993408921de8dea9d561f201d..e3c6794363cd6336effbeac83a179f3796dd71b0 100644
--- a/security/manager/ssl/nsICertOverrideService.idl
+++ b/security/manager/ssl/nsICertOverrideService.idl
@@ -137,7 +137,9 @@ interface nsICertOverrideService : nsISupports {
    *  @param aDisable If true, disable all security check and make
    *                  hasMatchingOverride always return true.
    */
-  void setDisableAllSecurityChecksAndLetAttackersInterceptMyData(in boolean aDisable);
+  void setDisableAllSecurityChecksAndLetAttackersInterceptMyData(
+      in boolean aDisable,
+      [optional] in uint32_t aUserContextId);
 
   readonly attribute boolean securityCheckDisabled;
 };
diff --git a/services/settings/Utils.sys.mjs b/services/settings/Utils.sys.mjs
index 12fef6cde815a9301944c399a58f27a7e4c4d5d7..0f7f06d1002a089547d1b15d7d8ddf264f28b529 100644
--- a/services/settings/Utils.sys.mjs
+++ b/services/settings/Utils.sys.mjs
@@ -97,7 +97,7 @@ const _cdnURLs = {};
 
 export var Utils = {
   get SERVER_URL() {
-    return lazy.allowServerURLOverride
+    return true || lazy.allowServerURLOverride
       ? lazy.gServerURL
       : AppConstants.REMOTE_SETTINGS_SERVER_URL;
   },
@@ -110,6 +110,9 @@ export var Utils = {
   log,
 
   get shouldSkipRemoteActivityDueToTests() {
+    // Playwright does not set Cu.isInAutomation, hence we just return true
+    // here in order to disable the remote activity.
+    return true;
     return (
       (lazy.isRunningTests || Cu.isInAutomation) &&
       this.SERVER_URL == "data:,#remote-settings-dummy/v1"
diff --git a/toolkit/components/browser/nsIWebBrowserChrome.idl b/toolkit/components/browser/nsIWebBrowserChrome.idl
index 75555352b8a15a50e4a21e34fc8ede4e9246c7cc..72855a404effa42b6c55cd0c2fcb8bdd6c2b3f9f 100644
--- a/toolkit/components/browser/nsIWebBrowserChrome.idl
+++ b/toolkit/components/browser/nsIWebBrowserChrome.idl
@@ -74,6 +74,9 @@ interface nsIWebBrowserChrome : nsISupports
     // Whether this window should use out-of-process cross-origin subframes.
     const unsigned long CHROME_FISSION_WINDOW         = 1 << 21;
 
+    // Whether this window has "width" or "height" defined in features
+    const unsigned long JUGGLER_WINDOW_EXPLICIT_SIZE  = 0x00400000;
+
     // Prevents new window animations on MacOS and Windows. Currently
     // ignored for Linux.
     const unsigned long CHROME_SUPPRESS_ANIMATION     = 1 << 24;
diff --git a/toolkit/components/enterprisepolicies/EnterprisePoliciesParent.sys.mjs b/toolkit/components/enterprisepolicies/EnterprisePoliciesParent.sys.mjs
index 00a5381133f8cec0de452c31c7151801a1acc0b9..5d3e3d6f566dc724f257beaeb994cedaa7e71139 100644
--- a/toolkit/components/enterprisepolicies/EnterprisePoliciesParent.sys.mjs
+++ b/toolkit/components/enterprisepolicies/EnterprisePoliciesParent.sys.mjs
@@ -108,6 +108,12 @@ EnterprisePoliciesManager.prototype = {
       Services.prefs.clearUserPref(PREF_POLICIES_APPLIED);
     }
 
+    // Playwright: Disable enterprise policies
+    if (true) {
+      this.status = Ci.nsIEnterprisePolicies.INACTIVE;
+      return;
+    }
+
     let provider = this._chooseProvider();
 
     if (provider.failed) {
diff --git a/toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp b/toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp
index 3aeddf503de749ecd2d87cac2e8185db0ae265d5..85f5f06ca3beee0b4aa6c51551bbe5a4390ed0df 100644
--- a/toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp
+++ b/toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp
@@ -487,7 +487,7 @@ void PopulateLanguages() {
   // sufficient to only collect this information as the other properties are
   // just reformats of Navigator::GetAcceptLanguages.
   nsTArray<nsString> languages;
-  dom::Navigator::GetAcceptLanguages(languages);
+  dom::Navigator::GetAcceptLanguages(nullptr, languages);
   nsCString output = "["_ns;
 
   for (const auto& language : languages) {
diff --git a/toolkit/components/startup/nsAppStartup.cpp b/toolkit/components/startup/nsAppStartup.cpp
index 76d85f007ba2198921f9deccfa91efc185af183b..689f0656debc6e50078828bde830c357cc7efaec 100644
--- a/toolkit/components/startup/nsAppStartup.cpp
+++ b/toolkit/components/startup/nsAppStartup.cpp
@@ -365,7 +365,7 @@ nsAppStartup::Quit(uint32_t aMode, int aExitCode, bool* aUserAllowedQuit) {
     nsCOMPtr<nsISimpleEnumerator> windowEnumerator;
     nsCOMPtr<nsIWindowMediator> mediator(
         do_GetService(NS_WINDOWMEDIATOR_CONTRACTID));
-    if (mediator) {
+    if (ferocity != eForceQuit && mediator) {
       mediator->GetEnumerator(nullptr, getter_AddRefs(windowEnumerator));
       if (windowEnumerator) {
         bool more;
diff --git a/toolkit/components/statusfilter/nsBrowserStatusFilter.cpp b/toolkit/components/statusfilter/nsBrowserStatusFilter.cpp
index 654903fadb709be976b72f36f155e23bc0622152..815b3dc24c9fda6b1db6c4666ac68904c87ac0ab 100644
--- a/toolkit/components/statusfilter/nsBrowserStatusFilter.cpp
+++ b/toolkit/components/statusfilter/nsBrowserStatusFilter.cpp
@@ -174,8 +174,8 @@ nsBrowserStatusFilter::OnStateChange(nsIWebProgress* aWebProgress,
 }
 
 NS_IMETHODIMP
-nsBrowserStatusFilter::OnProgressChange(nsIWebProgress* aWebProgress,
-                                        nsIRequest* aRequest,
+nsBrowserStatusFilter::OnProgressChange(nsIWebProgress *aWebProgress,
+                                        nsIRequest *aRequest,
                                         int32_t aCurSelfProgress,
                                         int32_t aMaxSelfProgress,
                                         int32_t aCurTotalProgress,
diff --git a/toolkit/components/windowwatcher/nsWindowWatcher.cpp b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
index 585a957fd8a1467dc262bd1ca2058584fd8762c9..16ad38c3b7d753c386e091af700d1bebd4c59e3e 100644
--- a/toolkit/components/windowwatcher/nsWindowWatcher.cpp
+++ b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
@@ -1875,7 +1875,11 @@ uint32_t nsWindowWatcher::CalculateChromeFlagsForContent(
 
   // Open a minimal popup.
   *aIsPopupRequested = true;
-  return nsIWebBrowserChrome::CHROME_MINIMAL_POPUP;
+  uint32_t chromeFlags = 0;
+  if (aFeatures.Exists("width") || aFeatures.Exists("height")) {
+    chromeFlags |= nsIWebBrowserChrome::JUGGLER_WINDOW_EXPLICIT_SIZE;
+  }
+  return chromeFlags | nsIWebBrowserChrome::CHROME_MINIMAL_POPUP;
 }
 
 /**
diff --git a/toolkit/mozapps/update/UpdateService.sys.mjs b/toolkit/mozapps/update/UpdateService.sys.mjs
index f7a6f11d510b895869673f842f29d9de9e433766..5be30f341b01acfe496a3178bef3f79282d5dfeb 100644
--- a/toolkit/mozapps/update/UpdateService.sys.mjs
+++ b/toolkit/mozapps/update/UpdateService.sys.mjs
@@ -3895,6 +3895,8 @@ export class UpdateService {
   }
 
   get disabledForTesting() {
+    /* playwright */
+    return true;
     return lazy.UpdateServiceStub.updateDisabledForTesting;
   }
 
diff --git a/toolkit/toolkit.mozbuild b/toolkit/toolkit.mozbuild
index f42ed17a4a75689ae9c8e769d7b6e2c3f654b8ee..5af0877335339407160dd7d10b89bd3d62adff9f 100644
--- a/toolkit/toolkit.mozbuild
+++ b/toolkit/toolkit.mozbuild
@@ -156,6 +156,7 @@ if CONFIG["ENABLE_WEBDRIVER"]:
         "/remote",
         "/testing/firefox-ui",
         "/testing/marionette",
+        "/juggler",
         "/toolkit/components/telemetry/tests/marionette",
     ]
 
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 318ee7e293b917534128d2c0fa631ecf369b5119..6049f5a260153f963710f45e6fd2345521e1180b 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -5640,7 +5640,10 @@ nsresult XREMain::XRE_mainRun() {
 
     if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
 #ifdef XP_MACOSX
-      if (!BackgroundTasks::IsBackgroundTaskMode()) {
+#    if defined(MOZ_BACKGROUNDTASKS)
+      if (!BackgroundTasks::IsBackgroundTaskMode())
+#    endif  // defined(MOZ_BACKGROUNDTASKS)
+      {
         rv = appStartup->CreateHiddenWindow();
         NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
       }
diff --git a/toolkit/xre/nsWindowsWMain.cpp b/toolkit/xre/nsWindowsWMain.cpp
index 7eb9e1104682d4eb47060654f43a1efa8b2a6bb2..a8315d6decf654b5302bea5beeea34140c300ded 100644
--- a/toolkit/xre/nsWindowsWMain.cpp
+++ b/toolkit/xre/nsWindowsWMain.cpp
@@ -14,8 +14,10 @@
 #endif
 
 #include "mozilla/Char16.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
 #include "nsUTF8Utils.h"
 
+#include <io.h>
 #include <windows.h>
 
 #ifdef __MINGW32__
@@ -114,6 +116,19 @@ static void FreeAllocStrings(int argc, char** argv) {
 int wmain(int argc, WCHAR** argv) {
   SanitizeEnvironmentVariables();
   SetDllDirectoryW(L"");
+  bool hasJugglerPipe =
+      mozilla::CheckArg(argc, argv, "juggler-pipe", nullptr,
+                        mozilla::CheckArgFlag::None) == mozilla::ARG_FOUND;
+  if (hasJugglerPipe && !mozilla::EnvHasValue("PW_PIPE_READ")) {
+    intptr_t stdio3 = _get_osfhandle(3);
+    intptr_t stdio4 = _get_osfhandle(4);
+    CHAR stdio3str[20];
+    CHAR stdio4str[20];
+    itoa(stdio3, stdio3str, 10);
+    itoa(stdio4, stdio4str, 10);
+    SetEnvironmentVariableA("PW_PIPE_READ", stdio3str);
+    SetEnvironmentVariableA("PW_PIPE_WRITE", stdio4str);
+  }
 
   // Only run this code if LauncherProcessWin.h was included beforehand, thus
   // signalling that the hosting process should support launcher mode.
diff --git a/uriloader/base/nsDocLoader.cpp b/uriloader/base/nsDocLoader.cpp
index 01ca680039edcc9f56900a40e0a94cb77a367383..36f3f9a13bc0e3da3285a7a14c824c1bad9a0799 100644
--- a/uriloader/base/nsDocLoader.cpp
+++ b/uriloader/base/nsDocLoader.cpp
@@ -812,6 +812,12 @@ void nsDocLoader::DocLoaderIsEmpty(bool aFlushLayout,
                       ("DocLoader:%p: Firing load event for document.open\n",
                        this));
 
+              nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+              if (os) {
+                nsIPrincipal* principal = doc->NodePrincipal();
+                if (!principal->IsSystemPrincipal())
+                  os->NotifyObservers(ToSupports(doc), "juggler-document-open-loaded", nullptr);
+              }
               // This is a very cut-down version of
               // nsDocumentViewer::LoadComplete that doesn't do various things
               // that are not relevant here because this wasn't an actual
diff --git a/uriloader/exthandler/nsExternalHelperAppService.cpp b/uriloader/exthandler/nsExternalHelperAppService.cpp
index 2c27ae5c68810557ab4b60efd4b4893433dff77d..29b1916903da6eebdbc38f987fda0d947c31e872 100644
--- a/uriloader/exthandler/nsExternalHelperAppService.cpp
+++ b/uriloader/exthandler/nsExternalHelperAppService.cpp
@@ -112,6 +112,7 @@
 
 #include "mozilla/Components.h"
 #include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ErrorNames.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ipc/URIUtils.h"
 
@@ -864,6 +865,12 @@ NS_IMETHODIMP nsExternalHelperAppService::ApplyDecodingForExtension(
   return NS_OK;
 }
 
+NS_IMETHODIMP nsExternalHelperAppService::SetDownloadInterceptor(
+    nsIDownloadInterceptor* interceptor) {
+  mInterceptor = interceptor;
+  return NS_OK;
+}
+
 nsresult nsExternalHelperAppService::GetFileTokenForPath(
     const char16_t* aPlatformAppPath, nsIFile** aFile) {
   nsDependentString platformAppPath(aPlatformAppPath);
@@ -1485,7 +1492,12 @@ nsresult nsExternalAppHandler::SetUpTempFile(nsIChannel* aChannel) {
   // Strip off the ".part" from mTempLeafName
   mTempLeafName.Truncate(mTempLeafName.Length() - ArrayLength(".part") + 1);
 
+  return CreateSaverForTempFile();
+}
+
+nsresult nsExternalAppHandler::CreateSaverForTempFile() {
   MOZ_ASSERT(!mSaver, "Output file initialization called more than once!");
+  nsresult rv;
   mSaver =
       do_CreateInstance(NS_BACKGROUNDFILESAVERSTREAMLISTENER_CONTRACTID, &rv);
   NS_ENSURE_SUCCESS(rv, rv);
@@ -1671,7 +1683,36 @@ NS_IMETHODIMP nsExternalAppHandler::OnStartRequest(nsIRequest* request) {
     return NS_OK;
   }
 
-  rv = SetUpTempFile(aChannel);
+  bool isIntercepted = false;
+  nsCOMPtr<nsIDownloadInterceptor> interceptor = mExtProtSvc->mInterceptor;
+  if (interceptor) {
+    nsCOMPtr<nsIFile> fileToUse;
+    rv = interceptor->InterceptDownloadRequest(this, request, mBrowsingContext, getter_AddRefs(fileToUse), &isIntercepted);
+    if (!NS_SUCCEEDED(rv)) {
+      LOG(("    failed to call nsIDowloadInterceptor.interceptDownloadRequest"));
+      return rv;
+    }
+    if (isIntercepted) {
+      LOG(("    request interceped by nsIDowloadInterceptor"));
+      if (fileToUse) {
+        mTempFile = fileToUse;
+        rv = mTempFile->GetLeafName(mTempLeafName);
+        NS_ENSURE_SUCCESS(rv, rv);
+      } else {
+        Cancel(NS_BINDING_ABORTED);
+        return NS_OK;
+      }
+    }
+  }
+
+  // Temp file is the final destination when download is intercepted. In that
+  // case we only need to create saver (and not create transfer later). Not creating
+  // mTransfer also cuts off all downloads handling logic in the js compoenents and
+  // browser UI.
+  if (isIntercepted)
+    rv = CreateSaverForTempFile();
+  else
+    rv = SetUpTempFile(aChannel);
   if (NS_FAILED(rv)) {
     nsresult transferError = rv;
 
@@ -1732,6 +1773,9 @@ NS_IMETHODIMP nsExternalAppHandler::OnStartRequest(nsIRequest* request) {
 
   bool alwaysAsk = true;
   mMimeInfo->GetAlwaysAskBeforeHandling(&alwaysAsk);
+  if (isIntercepted) {
+    return NS_OK;
+  }
   if (alwaysAsk) {
     // But we *don't* ask if this mimeInfo didn't come from
     // our user configuration datastore and the user has said
@@ -2248,6 +2292,16 @@ nsExternalAppHandler::OnSaveComplete(nsIBackgroundFileSaver* aSaver,
     NotifyTransfer(aStatus);
   }
 
+  if (!mCanceled) {
+    nsCOMPtr<nsIDownloadInterceptor> interceptor = mExtProtSvc->mInterceptor;
+    if (interceptor) {
+      nsCString noError;
+      nsresult rv = interceptor->OnDownloadComplete(this, noError);
+      MOZ_ASSERT(NS_SUCCEEDED(rv), "Failed to call nsIDowloadInterceptor.OnDownloadComplete");
+      Unused << rv;
+    }
+  }
+
   return NS_OK;
 }
 
@@ -2731,6 +2785,15 @@ NS_IMETHODIMP nsExternalAppHandler::Cancel(nsresult aReason) {
     }
   }
 
+  nsCOMPtr<nsIDownloadInterceptor> interceptor = mExtProtSvc->mInterceptor;
+  if (interceptor) {
+    nsCString errorName;
+    GetErrorName(aReason, errorName);
+    nsresult rv = interceptor->OnDownloadComplete(this, errorName);
+    MOZ_ASSERT(NS_SUCCEEDED(rv), "Failed notify nsIDowloadInterceptor about cancel");
+    Unused << rv;
+  }
+
   // Break our reference cycle with the helper app dialog (set up in
   // OnStartRequest)
   mDialog = nullptr;
diff --git a/uriloader/exthandler/nsExternalHelperAppService.h b/uriloader/exthandler/nsExternalHelperAppService.h
index 2dd4ff87bda3e0ba395cca168c42b37db1713ddf..83e8a3d328e325b3f50f593c9ea71692f9c7d401 100644
--- a/uriloader/exthandler/nsExternalHelperAppService.h
+++ b/uriloader/exthandler/nsExternalHelperAppService.h
@@ -258,6 +258,8 @@ class nsExternalHelperAppService : public nsIExternalHelperAppService,
       mozilla::dom::BrowsingContext* aContentContext, bool aForceSave,
       nsIInterfaceRequestor* aWindowContext,
       nsIStreamListener** aStreamListener);
+
+  nsCOMPtr<nsIDownloadInterceptor> mInterceptor;
 };
 
 /**
@@ -455,6 +457,9 @@ class nsExternalAppHandler final : public nsIStreamListener,
    * Upon successful return, both mTempFile and mSaver will be valid.
    */
   nsresult SetUpTempFile(nsIChannel* aChannel);
+
+  nsresult CreateSaverForTempFile();
+
   /**
    * When we download a helper app, we are going to retarget all load
    * notifications into our own docloader and load group instead of
diff --git a/uriloader/exthandler/nsIExternalHelperAppService.idl b/uriloader/exthandler/nsIExternalHelperAppService.idl
index 53ea934dd4876e4b491b724385c8fbf7d00ee6cd..0b7b88c853b21ce778d8e87fea0a2bfe839ad412 100644
--- a/uriloader/exthandler/nsIExternalHelperAppService.idl
+++ b/uriloader/exthandler/nsIExternalHelperAppService.idl
@@ -6,8 +6,11 @@
 
 #include "nsICancelable.idl"
 
+webidl BrowsingContext;
+interface nsIHelperAppLauncher;
 interface nsIURI;
 interface nsIChannel;
+interface nsIRequest;
 interface nsIStreamListener;
 interface nsIFile;
 interface nsIMIMEInfo;
@@ -15,6 +18,17 @@ interface nsIWebProgressListener2;
 interface nsIInterfaceRequestor;
 webidl BrowsingContext;
 
+/**
+ * Interceptor interface used by Juggler.
+ */
+[scriptable, uuid(9a20e9b0-75d0-11ea-bc55-0242ac130003)]
+interface nsIDownloadInterceptor : nsISupports
+{
+  boolean interceptDownloadRequest(in nsIHelperAppLauncher aHandler, in nsIRequest aRequest, in BrowsingContext aBrowsingContext, out nsIFile file);
+
+  void onDownloadComplete(in nsIHelperAppLauncher aHandler, in ACString aErrorName);
+};
+
 /**
  * The external helper app service is used for finding and launching
  * platform specific external applications for a given mime content type.
@@ -87,6 +101,8 @@ interface nsIExternalHelperAppService : nsISupports
    * `DownloadIntegration.sys.mjs`, which is implemented on all platforms.
    */
   nsIFile getPreferredDownloadsDirectory();
+
+  void setDownloadInterceptor(in nsIDownloadInterceptor interceptor);
 };
 
 /**
diff --git a/widget/InProcessCompositorWidget.cpp b/widget/InProcessCompositorWidget.cpp
index 1c25e9d9a101233f71e92288a0f93125b81ac1c5..22cf67b0f6e3ddd2b3ed725a314ba6a9896abd1c 100644
--- a/widget/InProcessCompositorWidget.cpp
+++ b/widget/InProcessCompositorWidget.cpp
@@ -4,7 +4,10 @@
 
 #include "InProcessCompositorWidget.h"
 
+#include "HeadlessCompositorWidget.h"
+#include "HeadlessWidget.h"
 #include "mozilla/VsyncDispatcher.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
 #include "nsBaseWidget.h"
 
 namespace mozilla {
@@ -23,6 +26,12 @@ RefPtr<CompositorWidget> CompositorWidget::CreateLocal(
   // do it after the static_cast.
   nsBaseWidget* widget = static_cast<nsBaseWidget*>(aWidget);
   MOZ_RELEASE_ASSERT(widget);
+  if (aInitData.type() ==
+      CompositorWidgetInitData::THeadlessCompositorWidgetInitData) {
+    return new HeadlessCompositorWidget(
+        aInitData.get_HeadlessCompositorWidgetInitData(), aOptions,
+        static_cast<HeadlessWidget*>(aWidget));
+  }
   return new InProcessCompositorWidget(aOptions, widget);
 }
 #endif
diff --git a/widget/MouseEvents.h b/widget/MouseEvents.h
index 413b3f00a9659a8d0760745a006bc72b3e4de846..3d26a1c5c1c9ff1feea698165085ae1a88517f86 100644
--- a/widget/MouseEvents.h
+++ b/widget/MouseEvents.h
@@ -363,6 +363,9 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
   // Otherwise, this must be 0.
   uint32_t mClickCount = 0;
 
+  // Unique event ID
+  uint32_t mJugglerEventId = 0;
+
   // Whether the event should ignore scroll frame bounds during dispatch.
   bool mIgnoreRootScrollFrame = false;
 
@@ -386,6 +389,7 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
     mContextMenuTrigger = aEvent.mContextMenuTrigger;
     mExitFrom = aEvent.mExitFrom;
     mClickCount = aEvent.mClickCount;
+    mJugglerEventId = aEvent.mJugglerEventId;
     mIgnoreRootScrollFrame = aEvent.mIgnoreRootScrollFrame;
     mIgnoreCapturingContent = aEvent.mIgnoreCapturingContent;
     mClickEventPrevented = aEvent.mClickEventPrevented;
diff --git a/widget/cocoa/NativeKeyBindings.mm b/widget/cocoa/NativeKeyBindings.mm
index e4bdf715e2fb899e97a5bfeb2e147127460d6047..3554f919480278b7353617481c7ce8050630a1aa 100644
--- a/widget/cocoa/NativeKeyBindings.mm
+++ b/widget/cocoa/NativeKeyBindings.mm
@@ -528,6 +528,13 @@
       break;
     case KEY_NAME_INDEX_ArrowLeft:
       if (aEvent.IsAlt()) {
+        if (aEvent.IsMeta() || aEvent.IsControl())
+          break;
+        instance->AppendEditCommandsForSelector(
+            !aEvent.IsShift()
+                ? ToObjcSelectorPtr(@selector(moveWordLeft:))
+                : ToObjcSelectorPtr(@selector(moveWordLeftAndModifySelection:)),
+            aCommands);
         break;
       }
       if (aEvent.IsMeta() || (aEvent.IsControl() && aEvent.IsShift())) {
@@ -550,6 +557,13 @@
       break;
     case KEY_NAME_INDEX_ArrowRight:
       if (aEvent.IsAlt()) {
+        if (aEvent.IsMeta() || aEvent.IsControl())
+          break;
+        instance->AppendEditCommandsForSelector(
+            !aEvent.IsShift()
+                ? ToObjcSelectorPtr(@selector(moveWordRight:))
+                : ToObjcSelectorPtr(@selector(moveWordRightAndModifySelection:)),
+            aCommands);
         break;
       }
       if (aEvent.IsMeta() || (aEvent.IsControl() && aEvent.IsShift())) {
@@ -572,6 +586,10 @@
       break;
     case KEY_NAME_INDEX_ArrowUp:
       if (aEvent.IsControl()) {
+        if (aEvent.IsMeta() || aEvent.IsAlt())
+          break;
+        instance->AppendEditCommandsForSelector(
+          ToObjcSelectorPtr(@selector(scrollPageUp:)), aCommands);
         break;
       }
       if (aEvent.IsMeta()) {
@@ -582,7 +600,7 @@
             !aEvent.IsShift()
                 ? ToObjcSelectorPtr(@selector(moveToBeginningOfDocument:))
                 : ToObjcSelectorPtr(
-                      @selector(moveToBegginingOfDocumentAndModifySelection:)),
+                      @selector(moveToBeginningOfDocumentAndModifySelection:)),
             aCommands);
         break;
       }
@@ -609,6 +627,10 @@
       break;
     case KEY_NAME_INDEX_ArrowDown:
       if (aEvent.IsControl()) {
+        if (aEvent.IsMeta() || aEvent.IsAlt())
+          break;
+        instance->AppendEditCommandsForSelector(
+          ToObjcSelectorPtr(@selector(scrollPageDown:)), aCommands);
         break;
       }
       if (aEvent.IsMeta()) {
diff --git a/widget/gtk/nsFilePicker.cpp b/widget/gtk/nsFilePicker.cpp
index 6f5b0ba67b59635256d444f6b56be656c0caac04..90815bb3d3ed2801fc2eba16db168f454dad9d67 100644
--- a/widget/gtk/nsFilePicker.cpp
+++ b/widget/gtk/nsFilePicker.cpp
@@ -21,6 +21,7 @@
 #include "mozilla/Components.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/Promise.h"
+#include "gfxPlatform.h"
 
 #include "nsArrayEnumerator.h"
 #include "nsEnumeratorUtils.h"
@@ -421,6 +422,11 @@ nsFilePicker::Open(nsIFilePickerShownCallback* aCallback) {
     return NS_OK;
   }
 
+  // Don't attempt to open a real file-picker in headless mode.
+  if (gfxPlatform::IsHeadless()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
   NS_ConvertUTF16toUTF8 title(mTitle);
 
   GtkWindow* parent_widget =
diff --git a/widget/headless/HeadlessCompositorWidget.cpp b/widget/headless/HeadlessCompositorWidget.cpp
index bb4ee9175e66dc40de1871a7f91368fe309494a3..747625e3869882300bfbc18b184db5151dd90c1a 100644
--- a/widget/headless/HeadlessCompositorWidget.cpp
+++ b/widget/headless/HeadlessCompositorWidget.cpp
@@ -3,6 +3,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#include "mozilla/layers/CompositorThread.h"
 #include "mozilla/widget/PlatformWidgetTypes.h"
 #include "HeadlessCompositorWidget.h"
 #include "VsyncDispatcher.h"
@@ -15,9 +16,32 @@ HeadlessCompositorWidget::HeadlessCompositorWidget(
     const layers::CompositorOptions& aOptions, HeadlessWidget* aWindow)
     : CompositorWidget(aOptions),
       mWidget(aWindow),
+      mMon("snapshotListener"),
       mClientSize(LayoutDeviceIntSize(aInitData.InitialClientSize()),
                   "HeadlessCompositorWidget::mClientSize") {}
 
+void HeadlessCompositorWidget::SetSnapshotListener(HeadlessWidget::SnapshotListener&& listener) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  ReentrantMonitorAutoEnter lock(mMon);
+  mSnapshotListener = std::move(listener);
+  layers::CompositorThread()->Dispatch(NewRunnableMethod(
+      "HeadlessCompositorWidget::PeriodicSnapshot", this,
+      &HeadlessCompositorWidget::PeriodicSnapshot
+  ));
+}
+
+already_AddRefed<gfx::DrawTarget> HeadlessCompositorWidget::StartRemoteDrawingInRegion(
+    const LayoutDeviceIntRegion& aInvalidRegion,
+    layers::BufferMode* aBufferMode) {
+  if (!mDrawTarget)
+    return nullptr;
+
+  *aBufferMode = layers::BufferMode::BUFFER_NONE;
+  RefPtr<gfx::DrawTarget> result = mDrawTarget;
+  return result.forget();
+}
+
 void HeadlessCompositorWidget::ObserveVsync(VsyncObserver* aObserver) {
   if (RefPtr<CompositorVsyncDispatcher> cvd =
           mWidget->GetCompositorVsyncDispatcher()) {
@@ -31,6 +55,59 @@ void HeadlessCompositorWidget::NotifyClientSizeChanged(
     const LayoutDeviceIntSize& aClientSize) {
   auto size = mClientSize.Lock();
   *size = aClientSize;
+  layers::CompositorThread()->Dispatch(NewRunnableMethod<LayoutDeviceIntSize>(
+      "HeadlessCompositorWidget::UpdateDrawTarget", this,
+      &HeadlessCompositorWidget::UpdateDrawTarget,
+      aClientSize));
+}
+
+void HeadlessCompositorWidget::UpdateDrawTarget(const LayoutDeviceIntSize& aClientSize) {
+  MOZ_ASSERT(NS_IsInCompositorThread());
+  if (aClientSize.IsEmpty()) {
+    mDrawTarget = nullptr;
+    return;
+  }
+
+  RefPtr<gfx::DrawTarget> old = std::move(mDrawTarget);
+  gfx::SurfaceFormat format = gfx::SurfaceFormat::B8G8R8A8;
+  gfx::IntSize size = aClientSize.ToUnknownSize();
+  mDrawTarget = mozilla::gfx::Factory::CreateDrawTarget(
+      mozilla::gfx::BackendType::SKIA, size, format);
+  if (old) {
+    RefPtr<gfx::SourceSurface> snapshot = old->Snapshot();
+    if (snapshot)
+      mDrawTarget->CopySurface(snapshot.get(), old->GetRect(), gfx::IntPoint(0, 0));
+  }
+}
+
+void HeadlessCompositorWidget::PeriodicSnapshot() {
+  ReentrantMonitorAutoEnter lock(mMon);
+  if (!mSnapshotListener)
+    return;
+
+  TakeSnapshot();
+  NS_DelayedDispatchToCurrentThread(NewRunnableMethod(
+      "HeadlessCompositorWidget::PeriodicSnapshot", this,
+      &HeadlessCompositorWidget::PeriodicSnapshot), 40);
+}
+
+void HeadlessCompositorWidget::TakeSnapshot() {
+  if (!mDrawTarget)
+    return;
+
+  RefPtr<gfx::SourceSurface> snapshot = mDrawTarget->Snapshot();
+  if (!snapshot) {
+    fprintf(stderr, "Failed to get snapshot of draw target\n");
+    return;
+  }
+
+  RefPtr<gfx::DataSourceSurface> dataSurface = snapshot->GetDataSurface();
+  if (!dataSurface) {
+    fprintf(stderr, "Failed to get data surface from snapshot\n");
+    return;
+  }
+
+  mSnapshotListener(std::move(dataSurface));
 }
 
 LayoutDeviceIntSize HeadlessCompositorWidget::GetClientSize() {
diff --git a/widget/headless/HeadlessCompositorWidget.h b/widget/headless/HeadlessCompositorWidget.h
index facd2bc65afab8ec1aa322faa20a67464964dfb9..d6dea95472bec6006411753c3dfdab2e3659171f 100644
--- a/widget/headless/HeadlessCompositorWidget.h
+++ b/widget/headless/HeadlessCompositorWidget.h
@@ -6,6 +6,7 @@
 #ifndef widget_headless_HeadlessCompositorWidget_h
 #define widget_headless_HeadlessCompositorWidget_h
 
+#include "mozilla/ReentrantMonitor.h"
 #include "mozilla/widget/CompositorWidget.h"
 
 #include "HeadlessWidget.h"
@@ -23,8 +24,12 @@ class HeadlessCompositorWidget final : public CompositorWidget,
                            HeadlessWidget* aWindow);
 
   void NotifyClientSizeChanged(const LayoutDeviceIntSize& aClientSize);
+  void SetSnapshotListener(HeadlessWidget::SnapshotListener&& listener);
 
   // CompositorWidget Overrides
+  already_AddRefed<gfx::DrawTarget> StartRemoteDrawingInRegion(
+      const LayoutDeviceIntRegion& aInvalidRegion,
+      layers::BufferMode* aBufferMode) override;
 
   uintptr_t GetWidgetKey() override;
 
@@ -42,10 +47,18 @@ class HeadlessCompositorWidget final : public CompositorWidget,
   }
 
  private:
+  void UpdateDrawTarget(const LayoutDeviceIntSize& aClientSize);
+  void PeriodicSnapshot();
+  void TakeSnapshot();
+
   HeadlessWidget* mWidget;
+  mozilla::ReentrantMonitor mMon;
 
   // See GtkCompositorWidget for the justification for this mutex.
   DataMutex<LayoutDeviceIntSize> mClientSize;
+
+  HeadlessWidget::SnapshotListener mSnapshotListener;
+  RefPtr<gfx::DrawTarget> mDrawTarget;
 };
 
 }  // namespace widget
diff --git a/widget/headless/HeadlessWidget.cpp b/widget/headless/HeadlessWidget.cpp
index c6095751bc1e9bbe907e64fb634b799cac31bb0a..ce1b995015843babeab0e3bf4e357d45066b3cab 100644
--- a/widget/headless/HeadlessWidget.cpp
+++ b/widget/headless/HeadlessWidget.cpp
@@ -111,6 +111,8 @@ void HeadlessWidget::Destroy() {
     }
   }
 
+  SetSnapshotListener(nullptr);
+
   nsBaseWidget::OnDestroy();
 
   nsBaseWidget::Destroy();
@@ -613,5 +615,14 @@ nsresult HeadlessWidget::SynthesizeNativeTouchpadPan(
   return NS_OK;
 }
 
+void HeadlessWidget::SetSnapshotListener(SnapshotListener&& listener) {
+  if (!mCompositorWidget) {
+    if (listener)
+      fprintf(stderr, "Trying to set SnapshotListener without compositor widget\n");
+    return;
+  }
+  mCompositorWidget->SetSnapshotListener(std::move(listener));
+}
+
 }  // namespace widget
 }  // namespace mozilla
diff --git a/widget/headless/HeadlessWidget.h b/widget/headless/HeadlessWidget.h
index 9856991ef32f25f51942f8cd664a09bec2192c70..948947a421179e91c51005aeb83ed0d18cfc84ce 100644
--- a/widget/headless/HeadlessWidget.h
+++ b/widget/headless/HeadlessWidget.h
@@ -141,6 +141,9 @@ class HeadlessWidget : public nsBaseWidget {
                                                int32_t aModifierFlags,
                                                nsIObserver* aObserver) override;
 
+  using SnapshotListener = std::function<void(RefPtr<gfx::DataSourceSurface>&&)>;
+  void SetSnapshotListener(SnapshotListener&& listener);
+
  private:
   ~HeadlessWidget();
   bool mEnabled;
diff --git a/widget/nsGUIEventIPC.h b/widget/nsGUIEventIPC.h
index cfededb82aa739c38f028bcaea0f3fa39d74f663..d3469a594f9e3b210d230c914de91da4cf9eff82 100644
--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -244,6 +244,7 @@ struct ParamTraits<mozilla::WidgetMouseEvent> {
                               aParam.mExitFrom.value()));
     }
     WriteParam(aWriter, aParam.mClickCount);
+    WriteParam(aWriter, aParam.mJugglerEventId);
   }
 
   static bool Read(MessageReader* aReader, paramType* aResult) {
@@ -268,6 +269,7 @@ struct ParamTraits<mozilla::WidgetMouseEvent> {
       aResult->mExitFrom = Some(static_cast<paramType::ExitFrom>(exitFrom));
     }
     rv = rv && ReadParam(aReader, &aResult->mClickCount);
+    rv = rv && ReadParam(aReader, &aResult->mJugglerEventId);
     return rv;
   }
 };
diff --git a/xpcom/reflect/xptinfo/xptinfo.h b/xpcom/reflect/xptinfo/xptinfo.h
index 787d30d881adedd57d2025ca57bff4bc6c57e803..ae1a0172c960ab16919133485722d2ae0cdbcbd4 100644
--- a/xpcom/reflect/xptinfo/xptinfo.h
+++ b/xpcom/reflect/xptinfo/xptinfo.h
@@ -505,7 +505,7 @@ static_assert(sizeof(nsXPTMethodInfo) == 8, "wrong size");
 #if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
 #  define PARAM_BUFFER_COUNT 18
 #else
-#  define PARAM_BUFFER_COUNT 14
+#  define PARAM_BUFFER_COUNT 15
 #endif
 
 /**
