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

chrome/renderer/resources/extensions/unload_event.js

 // Copyright 2013 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.
 
 // Special unload event. We don't use the DOM unload because that slows down
 // tab shutdown. On the other hand, onUnload might not always fire, since
 // Chrome will terminate renderers on shutdown (SuddenTermination).
 
 // Implement a primitive subset of the Event interface as needed, since if this
 // was to use the real event object there would be a circular dependency.
 var listeners = [];
 
 exports.addListener = function(listener) {
-  listeners.push(listener);
+  $Array.push(listeners, listener);
 };
 
 exports.removeListener = function(listener) {
   for (var i = 0; i < listeners.length; ++i) {
     if (listeners[i] == listener) {
-      listeners.splice(i, 1);
+      $Array.splice(listeners, i, 1);
       return;
     }
   }
 };
 
 exports.wasDispatched = false;
 
 // dispatch() is called from C++.
 exports.dispatch = function() {
   exports.wasDispatched = true;
   for (var i = 0; i < listeners.length; ++i)
     listeners[i]();
 };