feat(firefox): support context-level screencast api (#3555)

src/browserContext.ts

@@ -149,7 +149,7 @@ export abstract class BrowserContext extends EventEmitter {
     this._timeoutSettings.setDefaultTimeout(timeout);
   }
 
-  _enableScreencast(options: types.ContextScreencastOptions) {
+  async _enableScreencast(options: types.ContextScreencastOptions) {
     this._screencastOptions = options;
     fs.mkdirSync(path.dirname(options.dir), {recursive: true});
   }

src/firefox/ffBrowser.ts

@@ -323,6 +323,11 @@ export class FFBrowserContext extends BrowserContext {
     await this._browser._connection.send('Browser.setRequestInterception', { browserContextId: this._browserContextId || undefined, enabled: !!this._requestInterceptor });
   }
 
+  async _enableScreencast(options: types.ContextScreencastOptions): Promise<void> {
+    await super._enableScreencast(options);
+    await this._browser._connection.send('Browser.setScreencastOptions', Object.assign({}, options, { browserContextId: this._browserContextId || undefined}));
+  }
+
   async _doClose() {
     assert(this._browserContextId);
     await this._browser._connection.send('Browser.removeBrowserContext', { browserContextId: this._browserContextId });

src/firefox/ffPage.ts

@@ -32,6 +32,7 @@ import { FFNetworkManager } from './ffNetworkManager';
 import { Protocol } from './protocol';
 import { selectors } from '../selectors';
 import { rewriteErrorMessage } from '../utils/stackTrace';
+import { Screencast } from '../browserContext';
 
 const UTILITY_WORLD_NAME = '__playwright_utility_world__';
 
@@ -50,6 +51,7 @@ export class FFPage implements PageDelegate {
   private readonly _contextIdToContext: Map<string, dom.FrameExecutionContext>;
   private _eventListeners: RegisteredListener[];
   private _workers = new Map<string, { frameId: string, session: FFSession }>();
+  private readonly _idToScreencast = new Map<string, Screencast>();
 
   constructor(session: FFSession, browserContext: FFBrowserContext, opener: FFPage | null) {
     this._session = session;
@@ -82,6 +84,8 @@ export class FFPage implements PageDelegate {
       helper.addEventListener(this._session, 'Page.workerDestroyed', this._onWorkerDestroyed.bind(this)),
       helper.addEventListener(this._session, 'Page.dispatchMessageFromWorker', this._onDispatchMessageFromWorker.bind(this)),
       helper.addEventListener(this._session, 'Page.crashed', this._onCrashed.bind(this)),
+      helper.addEventListener(this._session, 'Page.screencastStarted', this._onScreencastStarted.bind(this)),
+      helper.addEventListener(this._session, 'Page.screencastStopped', this._onScreencastStopped.bind(this)),
     ];
     this._pagePromise = new Promise(f => this._pageCallback = f);
     session.once(FFSessionEvents.Disconnected, () => this._page._didDisconnect());
@@ -255,6 +259,20 @@ export class FFPage implements PageDelegate {
     this._page._didCrash();
   }
 
+  _onScreencastStarted(event: Protocol.Page.screencastStartedPayload) {
+    const screencast = new Screencast(event.file, this._page);
+    this._idToScreencast.set(event.uid, screencast);
+    this._browserContext.emit(Events.BrowserContext.ScreencastStarted, screencast);
+  }
+
+  _onScreencastStopped(event: Protocol.Page.screencastStoppedPayload) {
+    const screencast = this._idToScreencast.get(event.uid);
+    if (!screencast)
+      return;
+    this._idToScreencast.delete(event.uid);
+    this._browserContext.emit(Events.BrowserContext.ScreencastStopped, screencast);
+  }
+
   async exposeBinding(binding: PageBinding) {
     await this._session.send('Page.addBinding', { name: binding.name, script: binding.source });
   }

test/screencast.spec.ts

@@ -257,12 +257,12 @@ it.fail(options.CHROMIUM || (options.WEBKIT && WIN))('should capture css transfo
   }
 });
 
-it.fail(options.CHROMIUM || options.FIREFOX)('should fire start/stop events when page created/closed', async({browser, tmpDir, server, toImpl}) => {
+it.fail(options.CHROMIUM)('should fire start/stop events when page created/closed', async({browser, tmpDir, server, toImpl}) => {
   if (!toImpl)
    return;
   // Use server side of the context. All the code below also uses server side APIs.
   const context = toImpl(await browser.newContext());
-  context._enableScreencast({width: 640, height: 480, dir: tmpDir});
+  await context._enableScreencast({width: 640, height: 480, dir: tmpDir});
   expect(context._screencastOptions).toBeTruthy();
 
   const [startEvent, newPage] = await Promise.all([