[MD settings] idle load basic and advanced pages

chrome/test/data/webui/settings/settings_page_browsertest.js

 // Copyright 2015 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 Prototype for Settings page tests. */
 
 /** @const {string} Path to root from chrome/test/data/webui/settings/. */
 var ROOT_PATH = '../../../../../';
 
 // Polymer BrowserTest fixture.
@@ skipping 44 matching lines @@
    * @return {!PolymerElement} The PolymerElement for the page.
    */
   getPage: function(type) {
     var settingsUi = document.querySelector('settings-ui');
     assertTrue(!!settingsUi);
     var settingsMain = settingsUi.$$('settings-main');
     assertTrue(!!settingsMain);
     var pageType = 'settings-' + type + '-page';
     var page = settingsMain.$$(pageType);
     assertTrue(!!page);
+    var idleRender = page.$$('[is=settings-idle-render]')

[dpapad, 2017/01/31 23:10:13]

Can we be more specific in the selector, as follows? 
page.$$('template[is=settings-idle-render])

This makes it more obvious that a settings-idle-render attribute is only
expected in a <template> tag.

[dschuyler, 2017/01/31 23:53:03]

Done.

+    if (idleRender) {
+      idleRender.get();
+      Polymer.dom.flush();
+    }
     return page;
   },
 
   /**
    * @param {!PolymerElement} page The PolymerElement for the page containing
    *     |section|.
    * @param {string} section The settings page section, e.g. 'appearance'.
    * @return {Node|undefined} The DOM node for the section.
    */
   getSection: function(page, section) {
@@ skipping 34 matching lines @@
     // Any other stamped subpages should not be visible.
     var subpages = stampedChildren.filter(function(element) {
       return element.getAttribute('route-path') != 'default';
     });
     for (var subpage of subpages) {
       assertEquals(subpage.offsetHeight, 0, 'Expected subpage #' + subpage.id +
           ' in ' + section.section + ' not to be visible.');
     }
   },
 };