[MD Bookmarks] Add UI for Material Bookmarks.

chrome/test/data/webui/md_bookmarks/test_util.js

 // Copyright 2016 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.
 
 /**
- * Replace the current body of the test with a new element.
+ * Replace the current primary element of the test with a new element. Useful

[tsergeant, 2017/01/03 23:31:17]

As above, undo all changes to this file.

[jiaxi, 2017/01/04 02:50:16]

Done.

+ * as an alternative to PolymerTest.clearBody() which preserves styling.
  * @param {Element} element
  */
 function replaceBody(element) {
-  PolymerTest.clearBody();
-  document.body.appendChild(element);
+  var body = document.body;
+  while (body.children.length > 0)
+    body.removeChild(body.children[0]);
+  body.appendChild(element);
 }