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

chrome/renderer/resources/extensions/content_watcher.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.
 
 var contentWatcherNative = requireNative("contentWatcherNative");
 
 // Returns the indices in |cssSelectors| that match any element on the page.
 exports.FindMatchingSelectors = function(cssSelectors) {
   var result = []
   $Array.forEach(cssSelectors, function(selector, index) {
     try {
       if (document.querySelector(selector) != null)
-        result.push(index);
+        $Array.push(result, index);
     } catch (exception) {
       throw new Error("query Selector failed on '" + selector + "': " +
                       exception.stack);
     }
   });
   return result;
 };
 
 // Watches the page for all changes and calls FrameMutated (a C++ callback) in
 // response.
 var mutation_observer = new WebKitMutationObserver(
   contentWatcherNative.FrameMutated);
 
 // This runs once per frame, when the module is 'require'd.
 mutation_observer.observe(document, {
   childList: true,
   attributes: true,
   characterData: true,
   subtree: true});