Disables the ability to tab to navigation items when an overlay is displayed.

chrome/browser/resources/uber/uber.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.
 
 cr.define('uber', function() {
   var localStrings = new LocalStrings();
 
   /**
    * Options for how web history should be handled.
    */
@@ skipping 120 matching lines @@
     else if (e.data.method === 'stopInterceptingEvents')
       foregroundNavigation();
     else if (e.data.method === 'setPath')
       setPath(e.origin, e.data.params.path);
     else if (e.data.method === 'setTitle')
       setTitle(e.origin, e.data.params.title);
     else if (e.data.method === 'showPage')
       showPage(e.data.params.pageId, HISTORY_STATE_OPTION.PUSH);
     else if (e.data.method === 'navigationControlsLoaded')
       onNavigationControlsLoaded();
+    else if (e.data.method === 'enableNavigationItemTabbing')
+      setNavigationItemTabbing(true);
+    else if (e.data.method === 'disableNavigationItemTabbing')
+      setNavigationItemTabbing(false);
     else if (e.data.method === 'adjustToScroll')
       adjustToScroll(e.data.params);
     else if (e.data.method === 'mouseWheel')
       forwardMouseWheel(e.data.params);
     else
       console.error('Received unexpected message', e.data);
   }
 
   /**
    * Sends the navigation iframe to the background.
@@ skipping 172 matching lines @@
 
   /**
    * Forward scroll wheel events to subpages.
    * @param {Object} params Relevant parameters of wheel event.
    */
   function forwardMouseWheel(params) {
     var iframe = getSelectedIframe().querySelector('iframe');
     uber.invokeMethodOnWindow(iframe.contentWindow, 'mouseWheel', params);
   }
 
+  /**
+   * Enables or disables the ability to tab to the navigation items.
+   * @param {boolean} enabled If true, enables tabbing; if false, disables it.
+   */
+  function setNavigationItemTabbing(enabled) {
+    navFrame.firstChild.tabIndex = enabled ? 0 : -1;
+    if (enabled)
+      navFrame.firstChild.removeAttribute('aria-hidden');
+    else
+      navFrame.firstChild.setAttribute('aria-hidden', true);
+  }
+
   return {
     onLoad: onLoad,
     onPopHistoryState: onPopHistoryState
   };
 });
 
 window.addEventListener('popstate', uber.onPopHistoryState);
 document.addEventListener('DOMContentLoaded', uber.onLoad);