[Extensions] More bindings hardening

chrome/renderer/resources/extensions/browser_action_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 browserAction API.
 
 var binding = require('binding').Binding.create('browserAction');
 
 var setIcon = require('setIcon').setIcon;
 var getExtensionViews = requireNative('runtime').GetExtensionViews;
@@ skipping 16 matching lines @@
 
     if (lastError.hasError(chrome)) {
       callback();
     } else {
       var views = getExtensionViews(-1, 'POPUP');
       callback(views.length > 0 ? views[0] : null);
     }
   });
 });
 
-exports.binding = binding.generate();
+exports.$set('binding', binding.generate());