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

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 binding for the i18n API.
 
 var binding = require('binding').Binding.create('i18n');
 
 var i18nNatives = requireNative('i18n');
 var GetL10nMessage = i18nNatives.GetL10nMessage;
 
 binding.registerCustomHook(function(bindingsAPI, extensionId) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
   apiFunctions.setUpdateArgumentsPreValidate('getMessage', function() {
-    var args = Array.prototype.slice.call(arguments);
+    var args = $Array.slice(arguments);
 
     // The first argument is the message, and should be a string.
     var message = args[0];
     if (typeof(message) !== 'string') {
       console.warn(extensionId + ': the first argument to getMessage should ' +
                    'be type "string", was ' + message +
                    ' (type "' + typeof(message) + '")');
       args[0] = String(message);
     }
 
     return args;
   });
 
   apiFunctions.setHandleRequest('getMessage',
                                 function(messageName, substitutions) {
     return GetL10nMessage(messageName, substitutions, extensionId);
   });
 });
 
 exports.binding = binding.generate();