Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/devtools_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 devtools API.
 
-(function() {
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
-native function GetChromeHidden();
-
-GetChromeHidden().registerCustomHook('devtools', function(bindingsAPI) {
+chromeHidden.registerCustomHook('devtools', function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
   apiFunctions.setHandleRequest('getTabEvents', function(tabId) {
     var tabIdProxy = {};
     var functions = ['onPageEvent', 'onTabClose'];
     functions.forEach(function(name) {
       // Event disambiguation is handled by name munging.  See
       // chrome/browser/extensions/extension_devtools_events.h for the C++
       // equivalent of this logic.
       tabIdProxy[name] = new chrome.Event('devtools.' + tabId + '.' + name);
     });
     return tabIdProxy;
   });
 });
-
-})();