Set prototype for GuestView*.prototype to null.

extensions/renderer/resources/guest_view/guest_view.js

 // Copyright 2014 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.
 
 // This module implements a wrapper for a guestview that manages its
 // creation, attaching, and destruction.
 
 var CreateEvent = require('guestViewEvents').CreateEvent;
 var EventBindings = require('event_bindings');
 var GuestViewInternal = getInternalApi ?
@@ skipping 30 matching lines @@
   this.guestView = guestView;
   this.pendingAction = null;
   this.viewType = viewType;
   this.internalInstanceId = 0;
 
   this.setupOnResize();
 }
 
 // Prevent GuestViewImpl inadvertently inheriting code from the global Object,
 // allowing a pathway for executing unintended user code execution.
+// TODO(wjmaclean): Use utils.expose() here instead? Track down other issues
+// of Object inheritance. https://crbug.com/701034
 GuestViewImpl.prototype.__proto__ = null;
 
 // Possible states.
 GuestViewImpl.GuestState = {
   GUEST_STATE_START: 0,
   GUEST_STATE_CREATED: 1,
   GUEST_STATE_ATTACHED: 2
 };
 
 // Sets up the onResize property on the GuestView.
@@ skipping 292 matching lines @@
   var internal = privates(this).internal;
   return internal.id;
 };
 
 // Exports
 if (!apiBridge) {
   exports.$set('GuestView', GuestView);
   exports.$set('GuestViewImpl', GuestViewImpl);
   exports.$set('ResizeEvent', ResizeEvent);
 }