Fix issue with descendants of aria-activedescendant being marked as focusable.

third_party/WebKit/Source/modules/accessibility/AXObjectCacheImpl.cpp

 /*
  * Copyright (C) 2014, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 965 matching lines @@
 
     postNotification(obj, AXCheckedStateChanged);
 
     AXObject* listbox = obj->parentObjectUnignored();
     if (listbox && listbox->roleValue() == ListBoxRole)
         postNotification(listbox, AXSelectedChildrenChanged);
 }
 
 void AXObjectCacheImpl::handleActiveDescendantChanged(Node* node)
 {
+    // Changing the active descendant should trigger recomputing all
+    // cached values even if it doesn't result in a notification, because
+    // it can affect what's focusable or not.
+    m_modificationCount++;
+
     if (AXObject* obj = getOrCreate(node))
         obj->handleActiveDescendantChanged();
 }
 
 void AXObjectCacheImpl::handleAriaRoleChanged(Node* node)
 {
     if (AXObject* obj = getOrCreate(node)) {
         obj->updateAccessibilityRole();
         m_modificationCount++;
         obj->notifyIfIgnoredValueChanged();
@@ skipping 288 matching lines @@
     visitor->trace(m_document);
     visitor->trace(m_nodeObjectMapping);
 
     visitor->trace(m_objects);
     visitor->trace(m_notificationsToPost);
 
     AXObjectCache::trace(visitor);
 }
 
 } // namespace blink