diff --git a/src/browser.ts b/src/browser.ts
index 87b36f4ba7..137f7a40a5 100644
--- a/src/browser.ts
+++ b/src/browser.ts
@@ -15,14 +15,14 @@
  */
 
 import { BrowserContext, BrowserContextOptions } from './browserContext';
-import { EventEmitter } from './platform';
+import * as platform from './platform';
 
-export class Browser extends EventEmitter {
-  newContext(options?: BrowserContextOptions): Promise<BrowserContext> { throw new Error('Not implemented'); }
-  browserContexts(): BrowserContext[] { throw new Error('Not implemented'); }
-  defaultContext(): BrowserContext { throw new Error('Not implemented'); }
+export interface Browser extends platform.EventEmitterType {
+  newContext(options?: BrowserContextOptions): Promise<BrowserContext>;
+  browserContexts(): BrowserContext[];
+  defaultContext(): BrowserContext;
 
-  disconnect(): void { throw new Error('Not implemented'); }
-  isConnected(): boolean { throw new Error('Not implemented'); }
-  close(): Promise<void> { throw new Error('Not implemented'); }
+  disconnect(): void;
+  isConnected(): boolean;
+  close(): Promise<void>;
 }
diff --git a/src/chromium/crBrowser.ts b/src/chromium/crBrowser.ts
index 02ca37020b..3c1e5fcf36 100644
--- a/src/chromium/crBrowser.ts
+++ b/src/chromium/crBrowser.ts
@@ -24,7 +24,7 @@ import { Page, Worker } from '../page';
 import { CRTarget } from './crTarget';
 import { Protocol } from './protocol';
 import { CRPage } from './crPage';
-import * as browser from '../browser';
+import { Browser } from '../browser';
 import * as network from '../network';
 import * as types from '../types';
 import * as platform from '../platform';
@@ -38,7 +38,7 @@ export type CRConnectOptions = {
   transport?: ConnectionTransport;
 };
 
-export class CRBrowser extends browser.Browser {
+export class CRBrowser extends platform.EventEmitter implements Browser {
   _connection: CRConnection;
   _client: CRSession;
   private _defaultContext: BrowserContext;
diff --git a/src/firefox/ffBrowser.ts b/src/firefox/ffBrowser.ts
index 4d1cc66b3b..c03fbf1840 100644
--- a/src/firefox/ffBrowser.ts
+++ b/src/firefox/ffBrowser.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-import * as browser from '../browser';
+import { Browser } from '../browser';
 import { BrowserContext, BrowserContextOptions } from '../browserContext';
 import { Events } from '../events';
 import { assert, helper, RegisteredListener } from '../helper';
@@ -33,7 +33,7 @@ export type FFConnectOptions = {
   transport?: ConnectionTransport;
 };
 
-export class FFBrowser extends browser.Browser {
+export class FFBrowser extends platform.EventEmitter implements Browser {
   _connection: FFConnection;
   _targets: Map<string, Target>;
   private _defaultContext: BrowserContext;
diff --git a/src/webkit/wkBrowser.ts b/src/webkit/wkBrowser.ts
index cbe430cddf..551fcf6004 100644
--- a/src/webkit/wkBrowser.ts
+++ b/src/webkit/wkBrowser.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-import * as browser from '../browser';
+import { Browser } from '../browser';
 import { BrowserContext, BrowserContextOptions } from '../browserContext';
 import { assert, helper, RegisteredListener } from '../helper';
 import * as network from '../network';
@@ -26,13 +26,14 @@ import { Events } from '../events';
 import { Protocol } from './protocol';
 import { WKConnection, WKConnectionEvents, WKPageProxySession } from './wkConnection';
 import { WKPageProxy } from './wkPageProxy';
+import * as platform from '../platform';
 
 export type WKConnectOptions = {
   slowMo?: number,
   transport: ConnectionTransport;
 };
 
-export class WKBrowser extends browser.Browser {
+export class WKBrowser extends platform.EventEmitter implements Browser {
   readonly _connection: WKConnection;
   private readonly _defaultContext: BrowserContext;
   private readonly _contexts = new Map<string, BrowserContext>();
diff --git a/utils/doclint/check_public_api/Documentation.js b/utils/doclint/check_public_api/Documentation.js
index 87af1ed914..ab640ce59b 100644
--- a/utils/doclint/check_public_api/Documentation.js
+++ b/utils/doclint/check_public_api/Documentation.js
@@ -126,6 +126,7 @@ Documentation.Member = class {
    * @param {!Array<!Documentation.Member>} argsArray
    */
   constructor(kind, name, type, argsArray, comment = '', returnComment = '', required = true) {
+    if (name === 'code') debugger;
     this.kind = kind;
     this.name = name;
     this.type = type;
diff --git a/utils/doclint/check_public_api/JSBuilder.js b/utils/doclint/check_public_api/JSBuilder.js
index 95c8fd6753..f9623cc4f0 100644
--- a/utils/doclint/check_public_api/JSBuilder.js
+++ b/utils/doclint/check_public_api/JSBuilder.js
@@ -45,33 +45,40 @@ function checkSources(sources) {
   const checker = program.getTypeChecker();
   const sourceFiles = program.getSourceFiles();
   const errors = [];
+  const apiClassNames = new Set();
   /** @type {!Array<!Documentation.Class>} */
   const classes = [];
-  /** @type {!Map<string, string>} */
+  /** @type {!Map<string, string[]>} */
   const inheritance = new Map();
   sourceFiles.filter(x => !x.fileName.includes('node_modules')).map(x => visit(x));
-  const documentation = new Documentation(recreateClassesWithInheritance(classes, inheritance));
+  const documentation = new Documentation(recreateClassesWithInheritance(classes, inheritance).filter(cls => apiClassNames.has(cls.name)));
 
   return {errors, documentation};
 
   /**
    * @param {!Array<!Documentation.Class>} classes
-   * @param {!Map<string, string>} inheritance
+   * @param {!Map<string, string[]>} inheritance
    * @return {!Array<!Documentation.Class>}
    */
   function recreateClassesWithInheritance(classes, inheritance) {
     const classesByName = new Map(classes.map(cls => [cls.name, cls]));
     return classes.map(cls => {
       const membersMap = new Map();
-      for (let wp = cls; wp; wp = classesByName.get(inheritance.get(wp.name))) {
-        for (const member of wp.membersArray) {
+      const visit = cls => {
+        if (!cls)
+          return;
+        for (const member of cls.membersArray) {
           // Member was overridden.
           const memberId = member.kind + ':' + member.name;
           if (membersMap.has(memberId))
             continue;
           membersMap.set(memberId, member);
         }
-      }
+        const parents = inheritance.get(cls.name) || [];
+        for (const parent of parents)
+          visit(classesByName.get(parent));
+      };
+      visit(cls);
       return new Documentation.Class(expandPrefix(cls.name), Array.from(membersMap.values()));
     });
   }
@@ -80,7 +87,8 @@ function checkSources(sources) {
    * @param {!ts.Node} node
    */
   function visit(node) {
-    if (ts.isClassDeclaration(node) || ts.isClassExpression(node)) {
+    const fileName = node.getSourceFile().fileName;
+    if (ts.isClassDeclaration(node) || ts.isClassExpression(node) || ts.isInterfaceDeclaration(node)) {
       const symbol = node.name ? checker.getSymbolAtLocation(node.name) : node.symbol;
       let className = symbol.getName();
 
@@ -92,13 +100,12 @@ function checkSources(sources) {
       }
       if (className && !excludeClasses.has(className)) {
         classes.push(serializeClass(className, symbol, node));
-        const parentClassName = parentClass(node);
-        if (parentClassName)
-          inheritance.set(className, parentClassName);
+        inheritance.set(className, parentClasses(node));
         excludeClasses.add(className);
       }
     }
-    const fileName = node.getSourceFile().fileName;
+    if (fileName.endsWith('/api.ts') && ts.isExportSpecifier(node))
+      apiClassNames.add(expandPrefix((node.propertyName || node.name).text));
     if (!fileName.endsWith('platform.ts') && !fileName.includes('src/server/')) {
       // Only relative imports.
       if (ts.isImportDeclaration(node) && ts.isStringLiteral(node.moduleSpecifier)) {
@@ -126,17 +133,18 @@ function checkSources(sources) {
     ts.forEachChild(node, visit);
   }
 
-  function parentClass(classNode) {
+  function parentClasses(classNode) {
+    const parents = [];
     for (const herigateClause of classNode.heritageClauses || []) {
       for (const heritageType of herigateClause.types) {
         let expression = heritageType.expression;
         if (expression.kind === ts.SyntaxKind.PropertyAccessExpression)
           expression = expression.name;
         if (classNode.name.escapedText !== expression.escapedText)
-          return expression.escapedText;
+          parents.push(expression.escapedText);
       }
     }
-    return null;
+    return parents;
   }
 
   function serializeSymbol(symbol, circular = []) {
@@ -225,6 +233,8 @@ function checkSources(sources) {
     /** @type {!Array<!Documentation.Member>} */
     const members = classEvents.get(className) || [];
     for (const [name, member] of symbol.members || []) {
+      if (className === 'Error')
+        continue;
       if (name.startsWith('_'))
         continue;
       if (EventEmitter.prototype.hasOwnProperty(name))
diff --git a/utils/doclint/check_public_api/index.js b/utils/doclint/check_public_api/index.js
index 7c1d919ec6..90d2197d78 100644
--- a/utils/doclint/check_public_api/index.js
+++ b/utils/doclint/check_public_api/index.js
@@ -58,17 +58,9 @@ module.exports = async function lint(page, mdSources, jsSources) {
  * @return {!Documentation}
  */
 function filterJSDocumentation(jsSources, jsDocumentation) {
-  const apijs = jsSources.find(source => source.name() === 'api.ts');
-  let includedClasses = null;
-  if (apijs) {
-    const api = require(path.join(apijs.filePath(), '..', '..', 'lib', 'api.js'));
-    includedClasses = new Set(Object.keys(api).map(c => jsBuilder.expandPrefix(c)));
-  }
   // Filter private classes and methods.
   const classes = [];
   for (const cls of jsDocumentation.classesArray) {
-    if (includedClasses && !includedClasses.has(cls.name))
-      continue;
     const members = cls.membersArray.filter(member => !EXCLUDE_PROPERTIES.has(`${cls.name}.${member.name}`));
     classes.push(new Documentation.Class(cls.name, members));
   }