Use element.createShadowRoot since WebKitShadowRoot is deprecated.

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 26 matching lines @@
 
 window.addEventListener('DOMContentLoaded', function() {
   watchForTag('WEBVIEW', function(addedNode) { new WebView(addedNode); });
 });
 
 /**
  * @constructor
  */
 function WebView(node) {
   this.node_ = node;
-  var shadowRoot = new WebKitShadowRoot(node);
+  var shadowRoot = node.webkitCreateShadowRoot();
 
   this.objectNode_ = document.createElement('object');
   this.objectNode_.type = 'application/browser-plugin';
   // The <object> node fills in the <browser> container.
   this.objectNode_.style.width = '100%';
   this.objectNode_.style.height = '100%';
   WEB_VIEW_ATTRIBUTES.forEach(function(attributeName) {
     this.objectNode_.setAttribute(
         attributeName, this.node_.getAttribute(attributeName));
   }, this);
@@ skipping 78 matching lines @@
   var node = this.node_;
   this.objectNode_.addEventListener('-internal-' + eventname, function(e) {
     var evt = new Event(eventname);
     var detail = e.detail ? JSON.parse(e.detail) : {};
     attribs.forEach(function(attribName) {
       evt[attribName] = detail[attribName];
     });
     node.dispatchEvent(evt);
   });
 }