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

chrome/test/data/webui/md_history/history_toolbar_test.js

Index: chrome/test/data/webui/md_history/history_toolbar_test.js
diff --git a/chrome/test/data/webui/md_history/history_toolbar_test.js b/chrome/test/data/webui/md_history/history_toolbar_test.js
index 6910024eb12f97f2d3aa1bdf5c0304b42d455408..e7d7d16a0ae136f490f9633c77f382ac325f3510 100644
--- a/chrome/test/data/webui/md_history/history_toolbar_test.js
+++ b/chrome/test/data/webui/md_history/history_toolbar_test.js
@@ -93,9 +93,39 @@ cr.define('md_history.history_toolbar_test', function() {
         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', '');

[tsergeant, 2016/11/23 05:46:48]

This line is necessary to remove the ?q= from the URL. Otherwise, the query will
show up again when replaceApp() is called. I assume this is what is causing the
tests to fail.

(We probably should just reset the query state in the URL as part of replaceApp
to ensure this can never happen)

[calamity, 2016/11/24 06:45:18]

Good catch. Done.

       });
     });
   }