<webview> + <extensionview>: Create a maybeHandleMutation call into attributes

extensions/renderer/resources/guest_view/extension_view.js

 // Copyright 2015 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 the ExtensionView <extensionview>.
 
 var GuestViewContainer = require('guestViewContainer').GuestViewContainer;
 var ExtensionViewConstants =
     require('extensionViewConstants').ExtensionViewConstants;
 var ExtensionViewInternal =
@@ skipping 34 matching lines @@
   return params;
 };
 
 // This observer monitors mutations to attributes of the <extensionview>.
 ExtensionViewImpl.prototype.handleAttributeMutation = function(
     attributeName, oldValue, newValue) {
   if (!this.attributes[attributeName])
     return;
 
   // Let the changed attribute handle its own mutation;
-  this.attributes[attributeName].handleMutation(oldValue, newValue);
+  this.attributes[attributeName].maybeHandleMutation(oldValue, newValue);
 };
 
 ExtensionViewImpl.prototype.onElementDetached = function() {
   this.guest.destroy();
   this.attributes[ExtensionViewConstants.ATTRIBUTE_SRC].reset();
 };
 
 GuestViewContainer.registerElement(ExtensionViewImpl);
 
 // Exports.
-exports.ExtensionViewImpl = ExtensionViewImpl;
+exports.ExtensionViewImpl = ExtensionViewImpl;