[MD settings] scroll to section find host

chrome/test/data/webui/settings/basic_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 Suite of tests for the Settings basic page. */
 
 GEN_INCLUDE(['settings_page_browsertest.js']);
 
 /**
  * @constructor
@@ skipping 33 matching lines @@
         sections.push('defaultBrowser');
       else
         sections = sections.concat(['internet', 'device']);
 
       for (var i = 0; i < sections.length; i++) {
         var section = self.getSection(page, sections[i]);
         expectTrue(!!section);
         self.verifySubpagesHidden(section);
       }
     });
+
+    // This test checks for a regression that occurred with scrollToSection_
+    // failing to find its host element.
+    test('scroll to section', function() {
+      // Setting the page and section will cause a scrollToSection_.
+      self.getPage('basic').currentRoute = {
+        page: 'basic',
+        section: 'onStartup',
+        subpage: [],
+      };
+
+      return new Promise(function(resolve, reject) {
+        // This timeout should be longer than the one in main_page_behavior,

[Dan Beam, 2016/05/31 21:27:20]

can you just make scrollToSection_ return a Promise or dispatch an event for
testing or something?

[dschuyler, 2016/05/31 22:02:15]

In the 'or something' category I made the check independent
of the timeout value in scrollToSection_().

Done.

+        // scrollToSection_(). It may be removed if/when that timeout is
+        // removed.
+        setTimeout(resolve, 200);
+      });
+    });
   });
 
   // Run all registered tests.
   mocha.run();
 });