MD Settings: Change search engine add button to a paper-button

chrome/test/data/webui/settings/search_engines_page_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('settings_search_engines_page', function() {
   /**
    * @param {boolean} canBeDefault
    * @param {boolean} canBeEdited
    * @param {boolean} canBeRemoved
    * @return {!SearchEngine}
@@ skipping 310 matching lines @@
               querySelector('iron-list').items;
           assertEquals(
               searchEnginesInfo.extensions.length, extensionEntries.length);
         });
       });
 
       // Tests that the add search engine dialog opens when the corresponding
       // button is tapped.
       test('AddSearchEngineDialog', function() {
         assertFalse(!!page.$$('settings-search-engine-dialog'));
-        var addSearchEngineButton = page.$$('#addSearchEngine > a');
+        var addSearchEngineButton = page.$.addSearchEngine;
         assertTrue(!!addSearchEngineButton);
 
         MockInteractions.tap(addSearchEngineButton);
         Polymer.dom.flush();
         assertTrue(!!page.$$('settings-search-engine-dialog'));
       });
     });
   }
 
   function registerOmniboxExtensionEntryTests() {
@@ skipping 41 matching lines @@
 
   return {
     registerTests: function() {
       registerDialogTests();
       registerSearchEngineEntryTests();
       registerOmniboxExtensionEntryTests();
       registerPageTests();
     },
   };
 });