Adds AXExpandedChanged for general roles.

ui/accessibility/ax_enums.idl

 // Copyright 2014 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.
 
 // These should be kept in sync with third_party/WebKit/public/web/WebAXEnums.h
 // until the Chromium and Blink trees are merged.
 [camel_case_enum_to_string=true] namespace ui {
 
   // For new entries to the following three enums, also add to
   // chrome/common/extensions/api/automation.idl.
@@ skipping 14 matching lines @@
   enum AXEvent {
     activedescendantchanged,   // Web
     alert,
     aria_attribute_changed,    // Implicit
     autocorrection_occured,    // Unknown: http://crbug.com/392498
     blur,                      // Remove: http://crbug.com/392502
     checked_state_changed,     // Implicit
     children_changed,
     clicked,
     document_selection_changed,
+    expanded_changed,          // Web
     focus,
     hide,                      // Remove: http://crbug.com/392502
     hover,
     invalid_status_changed,    // Implicit
     layout_complete,           // Web
     live_region_changed,       // Web
     load_complete,             // Web
     location_changed,          // Web
     menu_end,                  // Native / Win
     menu_list_item_selected,   // Web
@@ skipping 405 matching lines @@
   };
 
   [cpp_enum_prefix_override="ax"] enum AXDescriptionFrom {
     description_from_uninitialized = 0,
     description_from_attribute,
     description_from_contents,
     description_from_placeholder,
     description_from_related_element
   };
 };