[Extensions] More bindings hardening

chrome/renderer/resources/extensions/declarative_content_custom_bindings.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.
 
 // Custom binding for the declarativeContent API.
 
 var binding = require('binding').Binding.create('declarativeContent');
 
 var utils = require('utils');
 var validate = require('schemaUtils').validate;
@@ skipping 55 matching lines @@
   };
   // TODO(rockot): Do not expose this in M39 stable. Making this restriction
   // possible will take some extra work. See http://crbug.com/415315
   declarativeContent.SetIcon = function(parameters) {
     setIcon(parameters, function (data) {
       setupInstance(this, data, 'SetIcon');
     }.bind(this));
   };
 });
 
-exports.binding = binding.generate();
+exports.$set('binding', binding.generate());