Implement a module system for the extension bindings JS.

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 bindings for the browserAction API.
 
-(function() {
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
-native function GetChromeHidden();
-
-GetChromeHidden().registerCustomHook('browserAction', function(bindingsAPI) {
+chromeHidden.registerCustomHook('browserAction', function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
   var setIcon = bindingsAPI.setIcon;
 
   apiFunctions.setHandleRequest('setIcon', function(details) {
     setIcon(details, this.name, this.definition.parameters, 'browser action');
   });
 });
-
-})();