[Local NTP] Add role="presentation" on the New Tab Page iframe.

chrome/browser/resources/local_ntp/local_ntp.js

 // Copyright 2013 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 The local InstantExtended NTP.
  */
 
 
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   // Container of tile contents.
   var innerElem = createAndAppendElement(tileElem, 'div', CLASSES.TILE_INNER);
 
   // The iframe which renders the page title.
   var titleElem = document.createElement('iframe');
   // Enable tab navigation on the iframe, which will move the selection to the
   // link element (which also has a tabindex).
   titleElem.tabIndex = '0';
 
+  // Make the iframe presentational for accessibility so screen readers perceive
+  // the iframe content as just part of the same page.
+  titleElem.setAttribute('role', 'presentation');
+
   // Why iframes have IDs:
   //
   // On navigating back to the NTP we see several onmostvisitedchange() events
   // in series with incrementing RIDs. After the first event, a set of iframes
   // begins loading RIDs n, n+1, ..., n+k-1; after the second event, these get
   // destroyed and a new set begins loading RIDs n+k, n+k+1, ..., n+2k-1.
   // Now due to crbug.com/68841, Chrome incorrectly loads the content for the
   // first set of iframes into the most recent set of iframes.
   //
   // Giving iframes distinct ids seems to cause some invalidation and prevent
@@ skipping 490 matching lines @@
 
 return {
   init: init,
   listen: listen
 };
 }
 
 if (!window.localNTPUnitTest) {
   LocalNTP().listen();
 }