Make the externally connectable browser test clobber all of the builtins,

chrome/renderer/resources/extensions/app_runtime_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 binding for the chrome.app.runtime API.
 
 var binding = require('binding').Binding.create('app.runtime');
 
 var eventBindings = require('event_bindings');
 var fileSystemHelpers = requireNative('file_system_natives');
 var GetIsolatedFileSystem = fileSystemHelpers.GetIsolatedFileSystem;
 var appNatives = requireNative('app_runtime');
 var DeserializeString = appNatives.DeserializeString;
 var SerializeToString = appNatives.SerializeToString;
 var CreateBlob = appNatives.CreateBlob;
 var entryIdManager = require('entryIdManager');
 
 eventBindings.registerArgumentMassager('app.runtime.onLaunched',
     function(args, dispatch) {
   var launchData = args[0];
 
   if (launchData && typeof launchData.id !== 'undefined') {
     // new-style dispatch.
     var items = []
     var numItems = launchData.items.length;
     var itemLoaded = function(err, item) {
       if (err) {
         console.error('Error getting fileEntry, code: ' + err.code);
       } else {
-        items.push(item);
+        $Array.push(items, item);
       }
       if (--numItems === 0) {
         if (items.length === 0) {
           dispatch([]);
         } else {
           var data = { id: launchData.id, items: items };
           dispatch([data]);
         }
       }
     };
     $Array.forEach(launchData.items, function(item) {
       var fs = GetIsolatedFileSystem(item.fileSystemId);
       fs.root.getFile(item.baseName, {}, function(fileEntry) {
         entryIdManager.registerEntry(item.entryId, fileEntry);
         itemLoaded(null, { entry: fileEntry, type: item.mimeType });
       }, function(fileError) {
         itemLoaded(fileError);
       });
     });
   } else if (launchData) {
     dispatch([launchData]);
   } else {
     dispatch([]);
   }
 });
 
 exports.binding = binding.generate();