Add an accessibility audit test for WebUI pages

chrome/test/data/webui/history_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.
 
 /** @const */ var TOTAL_RESULT_COUNT = 160;
 
 /**
  * Create a fake history result with the given timestamp.
  * @param {Number} timestamp Timestamp of the entry, in ms since the epoch.
  * @return {Object} An object representing a history entry.
@@ skipping 20 matching lines @@
 BaseHistoryWebUITest.prototype = {
   __proto__: testing.Test.prototype,
 
   /**
    * Browse to the history page & call our preLoad().
    */
   browsePreload: 'chrome://history-frame',
 
   isAsync: true,
 
+  runA11yChecks: false,
+  a11yIssuesAreErrors: false,
+
   /**
    * Register handlers to stub out calls to the history backend.
    * @override
    */
   preLoad: function() {
     // Mock4JS doesn't pass in the actual arguments to the stub, but it _will_
     // pass the original args to the matcher object. SaveMockArguments acts as
     // a proxy for another matcher, but keeps track of all the arguments it was
     // asked to match.
     var savedArgs = new SaveMockArguments();
@@ skipping 49 matching lines @@
 };
 
 TEST_F('BaseHistoryWebUITest', 'emptyHistory', function() {
   expectTrue($('newest-button').hidden);
   expectTrue($('newer-button').hidden);
   expectTrue($('older-button').hidden);
   testDone();
 });
 
 TEST_F('HistoryWebUITest', 'basicTest', function() {
+  enableA11yChecks();
+
   var resultCount = document.querySelectorAll('.entry').length;
 
   // Check that there are two days of entries.
   var dayHeaders = document.querySelectorAll('.day');
   assertEquals(2, dayHeaders.length);
   expectNotEquals(dayHeaders[0].textContent, dayHeaders[1].textContent);
+  expectAccessibilityOk();
 
   // Check that the entries in each day are time-ordered, and that no
   // duplicate URLs appear on a given day.
   var urlsByDay = {};
   var lastDate = new Date();
   for (var day = 0; day < dayHeaders.length; ++day) {
     var dayTitle = dayHeaders[day].textContent;
     var dayResults = document.querySelectorAll('.day-results')[day];
     var entries = dayResults.querySelectorAll('.entry');
     expectGT(entries.length, 0);
@@ skipping 54 matching lines @@
   // Go back to the first page, and check that the same day headers are there.
   $('newest-button').click();
   var newDayHeaders = document.querySelectorAll('.day');
   expectEquals(2, newDayHeaders.length);
   expectNotEquals(newDayHeaders[0].textContent, newDayHeaders[1].textContent);
   expectEquals(dayHeaders[0].textContent, newDayHeaders[0].textContent);
   expectEquals(dayHeaders[1].textContent, newDayHeaders[1].textContent);
 
   testDone();
 });