MD Settings: Lazy load the contents of the "advanced" settings.

chrome/test/data/webui/settings/help_page_browsertest.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 Material Help page tests. */
 
 GEN_INCLUDE(['settings_page_browsertest.js']);
 GEN('#include "base/command_line.h"');
 
 /**
  * @constructor
  * @extends {SettingsPageBrowserTest}
  */
 function SettingsHelpPageBrowserTest() {}
 
 SettingsHelpPageBrowserTest.prototype = {
   __proto__: SettingsPageBrowserTest.prototype,
 
   /** @override */
   browsePreload: 'chrome://help/',
 
   commandLineSwitches: [{switchName: 'enable-features',
                          switchValue: 'MaterialDesignSettings'}],
 
   /** @override */
   extraLibraries: PolymerTest.getLibraries(ROOT_PATH),
+
+  /** @override */
+  setUp: function() {
+    // Intentionally bypassing SettingsPageBrowserTest#setUp.
+    PolymerTest.prototype.setUp.call(this);
+  },
 };
 
 TEST_F('SettingsHelpPageBrowserTest', 'Load', function() {
   // Assign |self| to |this| instead of binding since 'this' in suite()
   // and test() will be a Mocha 'Suite' or 'Test' instance.
   var self = this;
 
   // Register mocha tests.
   suite('Help page', function() {
     test('about section', function() {
-      var page = self.getPage('about');
-      expectTrue(!!self.getSection(page, 'about'));
+      return self.getPage('about').then(function(page) {
+        expectTrue(!!self.getSection(page, 'about'));
+      });
     });
   });
 
   // Run all registered tests.
   mocha.run();
 });