MD Settings: Lazy-load sub-pages.

chrome/test/data/webui/settings/device_page_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.
 
 cr.define('settings_device_page', function() {
   /** @return {!DevicePageElement} */
   function getDevicePage() {
     var devicePage = document.createElement('settings-device-page');
     var page = this.getPage('basic');
     var deviceSection = this.getSection(page, 'device');
@@ skipping 35 matching lines @@
     }, {
       key: 'settings.language.remap_diamond_key_to',
       type: chrome.settingsPrivate.PrefType.NUMBER,
       value: 3,
     }, {
       key: 'settings.language.send_function_keys',
       type: chrome.settingsPrivate.PrefType.BOOLEAN,
       value: false,
     }];
 
-    test('keyboard subpage', function() {
-      var devicePage = document.createElement('settings-device-page');
+    var devicePage;
+
+    setup(function() {
+      devicePage = document.createElement('settings-device-page');
       devicePage.currentRoute = {page: 'basic', section: '', subpage: []};
       devicePage.prefs = fakePrefs;
+      Polymer.dom.flush();
+    });
 
+    test('keyboard subpage', function() {
       // Open the keyboard subpage.
       var keyboardRow = devicePage.$$('#main #keyboardRow');
       assertTrue(!!keyboardRow);
       MockInteractions.tap(keyboardRow);
       expectEquals(devicePage.currentRoute.section, 'device');
       expectEquals(devicePage.currentRoute.subpage[0], 'keyboard');
       var keyboardPage = devicePage.$$('#keyboard settings-keyboard');
       assertTrue(!!keyboardPage);
 
       // Initially, the optional keys are hidden.
@@ skipping 12 matching lines @@
       // Pretend a Caps Lock key is now available.
       showCapsLock = true;
       cr.webUIListenerCallback(
           'show-keys-changed', showCapsLock, showDiamondKey);
       Polymer.dom.flush();
       expectTrue(!!keyboardPage.$$('#capsLockKey'));
       expectTrue(!!keyboardPage.$$('#diamondKey'));
     });
   });
 });