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

chrome/test/data/webui/md_history/history_toolbar_test.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.
 
 cr.define('md_history.history_toolbar_test', function() {
   function registerTests() {
     suite('history-toolbar', function() {
       var app;
       var element;
       var toolbar;
@@ skipping 75 matching lines @@
         registerMessageCallback('queryHistory', this, function (info) {
           assertTrue(toolbar.spinnerActive);
           app.historyResult(createHistoryInfo(), TEST_HISTORY_RESULTS);
           assertFalse(toolbar.spinnerActive);
           done();
         });
 
         toolbar.$$('cr-toolbar').fire('search-changed', 'Test2');
       });
 
+      test('grouped history navigation buttons', function() {
+        var info = createHistoryInfo();
+        info.finished = false;
+        app.historyResult(info, []);
+        app.grouped_ = true;
+        return PolymerTest.flushTasks().then(function() {
+          app.set('queryState_.range', HistoryRange.MONTH);
+          groupedList = app.$.history.$$('#grouped-list');
+          assertTrue(!!groupedList);
+          var today = toolbar.$$('#today-button');
+          var next = toolbar.$$('#next-button');
+          var prev = toolbar.$$('#prev-button');
+
+          assertEquals(0, toolbar.groupedOffset);
+          assertTrue(today.disabled);
+          assertTrue(next.disabled);
+          assertFalse(prev.disabled);
+
+          MockInteractions.tap(prev);
+          assertEquals(1, toolbar.groupedOffset);
+          assertFalse(today.disabled);
+          assertFalse(next.disabled);
+          assertFalse(prev.disabled);
+
+          app.historyResult(createHistoryInfo(), []);
+          assertFalse(today.disabled);
+          assertFalse(next.disabled);
+          assertTrue(prev.disabled);
+        });
+      });
+
       teardown(function() {
         registerMessageCallback('queryHistory', this, function() {});
-        app.set('queryState_.searchTerm', '');
       });
     });
   }
   return {
     registerTests: registerTests
   };
 });
 
 
 cr.define('md_history.history_toolbar_focus_test', function() {
@@ skipping 40 matching lines @@
                   .isSearchFocused());
         });
       });
     });
   };
 
   return {
     registerTests: registerTests
   };
 });