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

chrome/test/data/webui/settings/route_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.
 
 suite('route', function() {
   /**
    * Returns a new promise that resolves after a window 'popstate' event.
    * @return {!Promise}
    */
   function whenPopState(causeEvent) {
     var promise = new Promise(function(resolve) {
       window.addEventListener('popstate', function callback() {
         window.removeEventListener('popstate', callback);
         resolve();
       });
     });
 
     causeEvent();
     return promise;
   }
 
+  teardown(function() {
+    PolymerTest.clearBody();
+  });
+
   /**
    * Tests a specific navigation situation.
    * @param {!settings.Route} previousRoute
    * @param {!settings.Route} currentRoute
    * @param {!settings.Route} expectedNavigatePreviousResult
    * @return {!Promise}
    */
   function testNavigateBackUsesHistory(previousRoute, currentRoute,
                                        expectedNavigatePreviousResult) {
     settings.navigateTo(previousRoute);
@@ skipping 146 matching lines @@
       // Path with a dash.
       assertEquals(
           settings.Route.KEYBOARD,
           settings.getRouteForPath('/keyboard-overlay'));
       assertEquals(
           settings.Route.KEYBOARD,
           settings.getRouteForPath('/keyboard-overlay/'));
     }
   });
 });