Use element.createShadowRoot since WebKitShadowRoot is deprecated.

chrome/test/data/extensions/api_test/shadow_dom/background.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.
 
 chrome.test.runTests([
-  function currentWindow() {
-    chrome.test.assertTrue('WebKitShadowRoot' in window);
-    chrome.test.succeed();
-  },
-
-  function newWindow() {
-    var w = window.open('empty.html');
-    chrome.test.assertTrue('WebKitShadowRoot' in w);
+  function createShadowRootIsAvailableInElement() {

[not at google - send to devlin, 2012/12/12 16:47:29]

when would this test fail?

[dougw, 2012/12/12 21:37:29]

For old versions of WebKit.

[not at google - send to devlin, 2012/12/12 21:45:37]

I don't follow... these tests run for WebKit at tip, so how could it fail?

+    chrome.test.assertTrue('webkitCreateShadowRoot' in Element.prototype);
     chrome.test.succeed();
   }
 ]);