Moving last app_view bits to extensions.

extensions/renderer/resources/app_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.
 
 var DocumentNatives = requireNative('document_natives');
 var GuestViewInternal =
     require('binding').Binding.create('guestViewInternal').generate();
 var IdGenerator = requireNative('id_generator');
 var guestViewInternalNatives = requireNative('guest_view_internal');
 
@@ skipping 185 matching lines @@
 
 var useCapture = true;
 window.addEventListener('readystatechange', function listener(event) {
   if (document.readyState == 'loading')
     return;
 
   registerBrowserPluginElement();
   registerAppViewElement();
   window.removeEventListener(event.type, listener, useCapture);
 }, useCapture);