Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/page_capture_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 pageCapture API.
 
-(function() {
+var pageCaptureNatives = requireNative('page_capture');
+var CreateBlob = pageCaptureNatives.CreateBlob;
+var SendResponseAck = pageCaptureNatives.SendResponseAck;
 
-native function GetChromeHidden();
-native function CreateBlob(filePath);
-native function SendResponseAck(requestId);
-
-var chromeHidden = GetChromeHidden();
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
 chromeHidden.registerCustomHook('pageCapture', function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
   apiFunctions.setCustomCallback('saveAsMHTML',
                                  function(name, request, response) {
     var params = chromeHidden.JSON.parse(response);
     var path = params.mhtmlFilePath;
     var size = params.mhtmlFileLength;
 
     if (request.callback)
       request.callback(CreateBlob(path, size));
     request.callback = null;
 
     // Notify the browser. Now that the blob is referenced from JavaScript,
     // the browser can drop its reference to it.
     SendResponseAck(request.id);
   });
 });
-
-})();