MD History: Delete button in the toolbar allows deletion of multiple history-items.

chrome/test/data/webui/md_history/history_card_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_card_test', function() {
   function registerTests() {
     suite('history-card', function() {
-      test('basic separator insertion', function(done) {
-        var element = document.createElement('history-card');
+      var spacers;
+      var element;
+      var items;

[calamity, 2016/02/04 23:59:52]

nit: remove spacers and items from here and just have them as local vars in
theirs tests.

+
+      suiteSetup(function() {
+        element = document.createElement('history-card');
         element.historyItems = [
           {"time": "1000000000"},
           {"time": "10000000"},
           {"time": "900000"}
         ];
+      })
+
+      test('basic separator insertion', function(done) {
         flush(function() {
           // Check that the correct number of time gaps are inserted.
-          var spacers =
+          spacers =
               Polymer.dom(element.root).querySelectorAll('#time-gap-separator');
           assertEquals(2, spacers.length);
           done();
         });
       });
+
+      test('separator insertion when items change but card stays the same',

[calamity, 2016/02/04 23:59:52]

'but item list length stays the same'

+          function(done) {
+        element.set('historyItems', [{"time": "900000"},
+                                     {"time": "900000"},
+                                     {"time": "900000"}]);
+
+        flush(function() {
+          items = Polymer.dom(element.root).querySelectorAll('history-item');
+          spacers =
+            Polymer.dom(element.root).querySelectorAll('#time-gap-separator');
+
+          assertEquals('900000', items[0].timestamp_);
+          assertEquals('900000', items[1].timestamp_);
+          assertEquals('900000', items[2].timestamp_);
+
+          // Note that the spacers aren't actually removed, are just set to:
+          // display: none;
+          for (var i = 0; i < spacers.length; i++) {
+            assertEquals(spacers[i].style.display, 'none');
+          }
+          done();
+        });
+      });
+
+      teardown(function() {
+        spacers = [];

[calamity, 2016/02/04 23:59:52]

You should be able to remove this.

+      });
     });
   }
   return {
     registerTests: registerTests
   };
 });