Implement declarative content script API for <webview> [js part].

chrome/test/data/extensions/platform_apps/web_view/shim/main.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var util = {};
 var embedder = {};
 embedder.baseGuestURL = '';
 embedder.emptyGuestURL = '';
 embedder.windowOpenGuestURL = '';
 embedder.noReferrerGuestURL = '';
@@ skipping 495 matching lines @@
     'onRequest',
     // WebRequest API.
     'onBeforeRequest',
     'onBeforeSendHeaders',
     'onSendHeaders',
     'onHeadersReceived',
     'onAuthRequired',
     'onBeforeRedirect',
     'onResponseStarted',
     'onCompleted',
-    'onErrorOccurred'
+    'onErrorOccurred',
+    // Declarative Content API.
+    'onPageChanged'
   ];
   var webview = document.createElement('webview');
   webview.setAttribute('partition', arguments.callee.name);
   webview.addEventListener('loadstop', function(e) {
     for (var i = 0; i < apiPropertiesToCheck.length; ++i) {
       embedder.test.assertEq('object',
                              typeof webview.request[apiPropertiesToCheck[i]]);
       embedder.test.assertEq(
           'function',
           typeof webview.request[apiPropertiesToCheck[i]].addListener);
@@ skipping 1550 matching lines @@
   'testFindAPI_findupdate': testFindAPI,
   'testLoadDataAPI': testLoadDataAPI
 };
 
 onload = function() {
   chrome.test.getConfig(function(config) {
     embedder.setUp_(config);
     chrome.test.sendMessage("Launched");
   });
 };