Don't expose document.register to Chrome Apps by default.

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.
 
 'use strict';
 
 var eventBindings = require('event_bindings');
+var DocumentNatives = requireNative('document_natives');
 var messagingNatives = requireNative('messaging_natives');
 var WebRequestEvent = require('webRequestInternal').WebRequestEvent;
 var webRequestSchema =
     requireNative('schema_registry').GetSchema('webRequest');
 
 // This secret enables hiding <webview> private members from the outside scope.
 // Outside of this file, |secret| is inaccessible. The only way to access the
 // <webview> element's internal members is via the |secret|. Since it's only
 // accessible by code here (and in web_view_experimental), only <webview>'s
 // API can access it and not external developers.
@@ skipping 646 matching lines @@
       this.webviewNode_,
       'request',
       {
         value: request,
         enumerable: true,
         writable: false
       }
   );
 };
 
-// Save document.register in a variable in case the developer attempts to
-// override it at some point.
-var register = document.register;
-
 // Registers browser plugin <object> custom element.
 function registerBrowserPluginElement() {
   var proto = Object.create(HTMLObjectElement.prototype);
 
   proto.createdCallback = function() {
     this.setAttribute('type', 'application/browser-plugin');
     // The <object> node fills in the <webview> container.
     this.style.width = '100%';
     this.style.height = '100%';
   };
 
   proto.attributeChangedCallback = function(name, oldValue, newValue) {
     if (!this.internal_) {
       return;
     }
     var internal = this.internal_(secret);
     internal.handleBrowserPluginAttributeMutation_(name, oldValue, newValue);
   };
 
   WebViewInternal.BrowserPlugin =
-      register.call(document, 'browser-plugin', {prototype: proto});
+      DocumentNatives.RegisterElement('browser-plugin', {prototype: proto});
 
   delete proto.createdCallback;
   delete proto.enteredDocumentCallback;
   delete proto.leftDocumentCallback;
   delete proto.attributeChangedCallback;
 }
 
 // Registers <webview> custom element.
 function registerWebViewElement() {
   var proto = Object.create(HTMLElement.prototype);
@@ skipping 46 matching lines @@
   proto.executeScript = function(var_args) {
     var internal = this.internal_(secret);
     $Function.apply(internal.executeScript_, internal, arguments);
   };
 
   proto.insertCSS = function(var_args) {
     var internal = this.internal_(secret);
     $Function.apply(internal.insertCSS_, internal, arguments);
   };
 
-  window.WebView = register.call(document, 'webview', {prototype: proto});
+  window.WebView =
+      DocumentNatives.RegisterElement('webview', {prototype: proto});
 
   // Delete the callbacks so developers cannot call them and produce unexpected
   // behavior.
   delete proto.createdCallback;
   delete proto.enteredDocumentCallback;
   delete proto.leftDocumentCallback;
   delete proto.attributeChangedCallback;
 }
 
 var useCapture = true;
@@ skipping 19 matching lines @@
 WebViewInternal.prototype.maybeGetWebviewExperimentalExtEvents_ = function() {};
 
 /**
  * Implemented when the experimental API is available.
  * @private
  */
 WebViewInternal.prototype.maybeAttachWebRequestEventToWebview_ = function() {};
 
 exports.WebViewInternal = WebViewInternal;
 exports.CreateEvent = createEvent;