Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/file_browser_private_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 fileBrowserPrivate API.
 
-(function() {
-
-native function GetChromeHidden();
-native function GetLocalFileSystem(name, path);
+var GetChromeHidden = natives.GetChromeHidden;
+var GetLocalFileSystem = natives.GetLocalFileSystem;
 
 var chromeHidden = GetChromeHidden();
 
 chromeHidden.registerCustomHook('fileBrowserPrivate', function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
   apiFunctions.setCustomCallback(
       "fileBrowserPrivate.requestLocalFileSystem",
       function(name, request, response) {
     var resp = response ? [chromeHidden.JSON.parse(response)] : [];
     var fs = null;
     if (!resp[0].error)
       fs = GetLocalFileSystem(resp[0].name, resp[0].path);
     if (request.callback)
       request.callback(fs);
     request.callback = null;
   });
 });
-
-})();