Added aria-hidden attribute to elements obscured behind an overlay to aid screen readers.

chrome/browser/resources/options2/options_page.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('options', function() {
   /////////////////////////////////////////////////////////////////////////////
   // OptionsPage class:
 
   /**
    * Base class for options page.
@@ skipping 216 matching lines @@
    * Shows a registered Overlay page. Does not update history.
    * @param {string} overlayName Page name.
    * @param {OptionPage} rootPage The currently visible root-level page.
    * @return {boolean} whether we showed an overlay.
    */
   OptionsPage.showOverlay_ = function(overlayName, rootPage) {
     var overlay = this.registeredOverlayPages[overlayName.toLowerCase()];
     if (!overlay || !overlay.canShowPage())
       return false;
 
+    // The current topmost page will soon be obscured behind the new overlay
+    // to be shown. To prevent screen readers from reading this "hidden"
+    // information, enable the aria-hidden attribute on this page.
+    var topmostPage = this.getTopmostVisiblePage();

[Evan Stade, 2012/05/09 22:37:37]

seems like this might do the wrong thing in certain cases, such as if you called
showOverlay twice on the same overlay (which can probably happen). Or if you
call showOverlay while dialog A is showing, then call showOverlay on dialog B,
then showOverlay on A again. A will still have aria-hidden on true. 

[Kyle Horimoto, 2012/05/10 22:18:46]

Done.

+    topmostPage.pageDiv.setAttribute('aria-hidden', true);
+
     if ((!rootPage || !rootPage.sticky) && overlay.parentPage)
       this.showPageByName(overlay.parentPage.name, false);
 
     if (!overlay.visible) {
       overlay.visible = true;
       if (overlay.didShowPage) overlay.didShowPage();
     }
 
     // Update tab title.
     this.setTitle_(overlay.title);
@@ skipping 32 matching lines @@
    */
   OptionsPage.closeOverlay = function() {
     var overlay = this.getVisibleOverlay_();
     if (!overlay)
       return;
 
     overlay.visible = false;
 
     if (overlay.didClosePage) overlay.didClosePage();
     this.updateHistoryState_(false, {ignoreHash: true});
+
+    // Since there is now a new topmost page, disable its aria-hidden attribute
+    // to allow screen readers to read its contents.
+    var topmostPage = this.getTopmostVisiblePage();
+    topmostPage.pageDiv.removeAttribute('aria-hidden');
   };
 
   /**
    * Cancels (closes) the overlay, due to the user pressing <Esc>.
    */
   OptionsPage.cancelOverlay = function() {
     // Blur the active element to ensure any changed pref value is saved.
     document.activeElement.blur();
     var overlay = this.getVisibleOverlay_();
     // Let the overlay handle the <Esc> if it wants to.
@@ skipping 557 matching lines @@
     canShowPage: function() {
       return true;
     },
   };
 
   // Export
   return {
     OptionsPage: OptionsPage
   };
 });