[Extensions] More bindings hardening

chrome/renderer/resources/extensions/tabs_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 tabs API.
 
 var binding = require('binding').Binding.create('tabs');
 
 var messaging = require('messaging');
 var tabsNatives = requireNative('tabs');
@@ skipping 35 matching lines @@
       forEach(options, function(k, v) {
         connectInfo[k] = v;
       });
     }
 
     var port = tabs.connect(tabId, connectInfo);
     messaging.sendMessageImpl(port, message, responseCallback);
   });
 });
 
-exports.binding = binding.generate();
+exports.$set('binding', binding.generate());