Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/i18n_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 i18n API.
 
 (function() {
 
-native function GetChromeHidden();
-native function GetL10nMessage();
+var natives = requireNative('i18n');
+var GetL10nMessage = natives.GetL10nMessage;
 
-GetChromeHidden().registerCustomHook('i18n',
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
+
+chromeHidden.registerCustomHook('i18n',
                                      function(bindingsAPI, extensionId) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
   apiFunctions.setHandleRequest('i18n.getMessage',
                                 function(messageName, substitutions) {
     return GetL10nMessage(messageName, substitutions, extensionId);
   });
 });
 
 })();