print preview: more voice feedback issues.

chrome/browser/resources/print_preview/previewarea/preview_area.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.
 
 /**
  * @typedef {{accessibility: Function,
  *            documentLoadComplete: Function,
  *            getHeight: Function,
  *            getHorizontalScrollbarThickness: Function,
  *            getPageLocationNormalized: Function,
@@ skipping 501 matching lines @@
 
     /**
      * Set the visibility of the message overlay.
      * @param {boolean} visible Whether to make the overlay visible or not
      * @private
      */
     setOverlayVisible_: function(visible) {
       this.overlayEl_.classList.toggle(
           PreviewArea.Classes_.INVISIBLE,
           !visible);
+      this.overlayEl_.setAttribute('aria-hidden', !visible);
 
       // Hide/show all controls that will overlap when the overlay is visible.
       var marginControls = this.getElement().getElementsByClassName(
           PreviewArea.Classes_.MARGIN_CONTROL);
       for (var i = 0; i < marginControls.length; ++i) {
         marginControls[i].classList.toggle(PreviewArea.Classes_.OVERLAYED,
                                            visible);
       }
       var previewAreaControls = this.getElement().getElementsByClassName(
           PreviewArea.Classes_.PREVIEW_AREA);
@@ skipping 261 matching lines @@
             new print_preview.Size(viewportWidth, viewportHeight));
       }
     }
   };
 
   // Export
   return {
     PreviewArea: PreviewArea
   };
 });