Run shim's watchForTag on document.DOMContentLoaded

chrome/renderer/resources/extensions/web_view.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.
 
 // Shim that simulates a <webview> tag via Mutation Observers.
 //
 // The actual tag is implemented via the browser plugin. The internals of this
 // are hidden via Shadow DOM.
 
 var watchForTag = require('tagWatcher').watchForTag;
@@ skipping 25 matching lines @@
   'loadabort' : ['url', 'isTopLevel', 'reason'],
   'loadcommit' : ['url', 'isTopLevel'],
   'loadredirect' : ['oldUrl', 'newUrl', 'isTopLevel'],
   'loadstart' : ['url', 'isTopLevel'],
   'loadstop' : [],
   'responsive' : ['processId'],
   'sizechanged': ['oldHeight', 'oldWidth', 'newHeight', 'newWidth'],
   'unresponsive' : ['processId']
 };
 
-window.addEventListener('DOMContentLoaded', function() {
-  watchForTag('WEBVIEW', function(addedNode) { new WebView(addedNode); });
-});
+// The <webview> tags we wish to watch for (watchForTag) does not belong to the
+// current scope's "document" reference. We need to wait until the document
+// begins loading, since only then will the "document" reference
+// point to the page's document (it will be reset between now and then).
+// We can't listen for the "readystatechange" event on the document (because
+// the object that it's dispatched on doesn't exist yet), but we can instead
+// do it at the window level in the capturing phase.
+window.addEventListener('readystatechange', function(e) {
+  if (document.readyState != 'loading') {
+    return;
+  }
+
+  document.addEventListener('DOMContentLoaded', function(e) {
+    watchForTag('WEBVIEW', function(addedNode) { new WebView(addedNode); });
+  });
+}, true /* useCapture */);
 
 /**
  * @constructor
  */
 function WebView(webviewNode) {
   this.webviewNode_ = webviewNode;
   this.browserPluginNode_ = this.createBrowserPluginNode_();
   var shadowRoot = this.webviewNode_.webkitCreateShadowRoot();
   shadowRoot.appendChild(this.browserPluginNode_);
 
@@ skipping 413 matching lines @@
   return [];
 };
 
 /**
  * Implemented when the experimental API is available.
  * @private
  */
 WebView.prototype.maybeSetupExperimentalAPI_ = function() {};
 
 exports.WebView = WebView;