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

chrome/renderer/resources/extensions/sync_file_system_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 syncFileSystem API.
 
 var binding = require('binding').Binding.create('syncFileSystem');
 
 var eventBindings = require('event_bindings');
 var fileSystemNatives = requireNative('file_system_natives');
@@ skipping 11 matching lines @@
     });
   }
   $Array.forEach(['getFileStatus'], bindFileEntryFunction);
 
   // Functions which take in an [instanceOf=EntryArray].
   function bindFileEntryArrayFunction(functionName) {
     apiFunctions.setUpdateArgumentsPostValidate(
         functionName, function(entries, callback) {
       var fileSystemUrlArray = [];
       for (var i=0; i < entries.length; i++) {
-        fileSystemUrlArray.push(entries[i].toURL());
+        $Array.push(fileSystemUrlArray, entries[i].toURL());
       }
       return [fileSystemUrlArray, callback];
     });
   }
   $Array.forEach(['getFileStatuses'], bindFileEntryArrayFunction);
 
   // Functions which take in an [instanceOf=DOMFileSystem].
   function bindFileSystemFunction(functionName) {
     apiFunctions.setUpdateArgumentsPostValidate(
         functionName, function(filesystem, callback) {
@@ skipping 26 matching lines @@
         var result = {};
         var entry = response[i].entry;
         result.fileEntry = fileSystemNatives.GetFileEntry(
             entry.fileSystemType,
             entry.fileSystemName,
             entry.rootUrl,
             entry.filePath,
             entry.isDirectory);
         result.status = response[i].status;
         result.error = response[i].error;
-        results.push(result);
+        $Array.push(results, result);
       }
     }
     if (request.callback)
       request.callback(results);
     request.callback = null;
   });
 });
 
 eventBindings.registerArgumentMassager(
     'syncFileSystem.onFileStatusChanged', function(args, dispatch) {
@@ skipping 10 matching lines @@
   fileInfo.fileEntry = fileEntry;
   fileInfo.status = args[1];
   if (fileInfo.status == "synced") {
     fileInfo.action = args[2];
     fileInfo.direction = args[3];
   }
   dispatch([fileInfo]);
 });
 
 exports.binding = binding.generate();