Using the new webkit CSS change notification instead of a mutation observer.

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 |css_selectors| that match any element on the page.
 exports.FindMatchingSelectors = function(css_selectors) {
   var result = []
   css_selectors.forEach(function(selector, index) {
     try {
       if (document.querySelector(selector) != null)
         result.push(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});