MD WebUI: Use dom-if to control hidden elements in <cr-toolbar>

chrome/test/data/webui/cr_elements/cr_toolbar_search_field_tests.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.
 
 /** @fileoverview Suite of tests for cr-toolbar-search-field. */
 cr.define('cr_toolbar_search_field', function() {
   function registerTests() {
     suite('cr-toolbar-search-field', function() {
       /** @type {?CrToolbarSearchFieldElement} */
       var field = null;
@@ skipping 37 matching lines @@
 
         MockInteractions.pressAndReleaseKeyOn(
             field.$.searchInput, 27, '', 'Escape');
         assertFalse(field.showingSearch, 'Pressing escape closes field.');
         assertNotEquals(field.$.searchInput, field.root.activeElement);
       });
 
       test('notifies on new searches', function() {
         MockInteractions.tap(field);
         simulateSearch('query1');
+        Polymer.dom.flush();
         assertEquals('query1', field.getValue());
 
-        MockInteractions.tap(field.$.clearSearch);
+        MockInteractions.tap(field.$$('#clearSearch'));
         assertFalse(field.showingSearch);
         assertEquals('', field.getValue());
 
         simulateSearch('query2');
         // Expecting identical query to be ignored.
         simulateSearch('query2');
 
         assertEquals(['query1', '', 'query2'].join(), searches.join());
       });
 
@@ skipping 14 matching lines @@
         MockInteractions.blur(field.$.searchInput);
 
         assertTrue(field.showingSearch);
       });
 
       test('opens when value is changed', function() {
         // Change search value without explicity opening the field first.
         // Similar to what happens when pasting or dragging into the input
         // field.
         simulateSearch('test');
+        Polymer.dom.flush();
 
-        assertFalse(field.$.clearSearch.hidden);
+        var clearSearch = field.$$('#clearSearch');
+        assertFalse(clearSearch.hidden);
         assertTrue(field.showingSearch);
 
-        MockInteractions.tap(field.$.clearSearch);
+        MockInteractions.tap(clearSearch);
         assertFalse(field.showingSearch);
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });