[Extensions] More bindings hardening

chrome/renderer/resources/extensions/chrome_direct_setting.js

 // Copyright 2013 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 Event = require('event_bindings').Event;
 var sendRequest = require('sendRequest').sendRequest;
 var validate = require('schemaUtils').validate;
 
 function extendSchema(schema) {
   var extendedSchema = $Array.slice(schema);
@@ skipping 23 matching lines @@
     validate([details, callback], clearSchema);
     return sendRequest('types.private.ChromeDirectSetting.clear',
                        [prefKey, details, callback],
                        extendSchema(clearSchema));
   };
   this.onChange = new Event('types.private.ChromeDirectSetting.' +
                             prefKey +
                             '.onChange');
 };
 
-exports.ChromeDirectSetting = ChromeDirectSetting;
+exports.$set('ChromeDirectSetting', ChromeDirectSetting);