[MD History] Make forward/backward work in grouped mode.

chrome/test/data/webui/md_history/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 primary element of the test with a new element. Useful
  * as an alternative to PolymerTest.clearBody() which preserves styling.
  * @param {Element} element
  */
 function replaceBody(element) {
   var body = document.body;
-  var currentBody =
-      body.querySelector('history-app') || body.querySelector('.test-body');
+  var app = body.querySelector('history-app');
+  // Clear the query on the app, if it exists. This clears any query in the URL.
+  if (app)
+    app.set('queryState_.searchTerm', '');
+
+  var currentBody = app || body.querySelector('.test-body');
   body.removeChild(currentBody);
 
   element.classList.add('test-body');
   body.appendChild(element);
 }
 
 /**
  * Replace the document body with a new instance of <history-app>.
  * @return {HistoryAppElement} The app which was created.
  */
@@ skipping 161 matching lines @@
   var tabs = tabUrls.map(function(tabUrl) {
     return {sessionId: 456, timestamp: 0, title: tabUrl, url: tabUrl};
   });
 
   return {
     tabs: tabs,
     sessionId: '123',
     userVisibleTimestamp: "A while ago"
   };
 }