Enable a11y audits and fix issues for help page.

chrome/browser/ui/webui/help/help_browsertest.js

 // Copyright (c) 2012 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.
 
 /**
  * TestFixture for extension settings WebUI testing.
  * @extends {testing.Test}
  * @constructor
  */
 function HelpPageWebUITest() {}
 
 HelpPageWebUITest.prototype = {
   __proto__: testing.Test.prototype,
 
+  /** @override */
+  runAccessibilityChecks: true,
+
+  /** @override */
+  accessibilityIssuesAreErrors: true,
+
   browsePreload: 'chrome://help-frame/',
 };
 
 // Test opening extension settings has correct location.
 TEST_F('HelpPageWebUITest', 'testOpenHelpPage', function() {
   assertEquals(this.browsePreload, document.location.href);
 });
 
 GEN('#if defined(OS_LINUX) || defined(GOOGLE_CHROME_BUILD)');
 
@@ skipping 57 matching lines @@
   help.HelpPage.setUpdateStatus('nearly_updated', '');
   expectFalse(container.hidden);
   expectTrue(update.hidden);
 
   help.HelpPage.setUpdateStatus('updated', '');
   expectFalse(container.hidden);
   expectTrue(!update.hidden && update.disabled);
 });
 
 GEN('#endif');