Don't post accessibility notification on object in detached document.

Source/core/accessibility/AXObjectCache.cpp

 /*
  * Copyright (C) 2008, 2009, 2010 Apple 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 604 matching lines @@
     RefPtr<Document> protectorForCacheOwner(m_document);
 
     m_notificationPostTimer.stop();
 
     unsigned i = 0, count = m_notificationsToPost.size();
     for (i = 0; i < count; ++i) {
         AccessibilityObject* obj = m_notificationsToPost[i].first.get();
         if (!obj->axObjectID())
             continue;
 
+        if (!obj->axObjectCache())
+            continue;
+
 #ifndef NDEBUG
         // Make sure none of the render views are in the process of being layed out.
         // Notifications should only be sent after the renderer has finished
         if (obj->isAccessibilityRenderObject()) {
             AccessibilityRenderObject* renderObj = static_cast<AccessibilityRenderObject*>(obj);
             RenderObject* renderer = renderObj->renderer();
             if (renderer && renderer->view())
                 ASSERT(!renderer->view()->layoutState());
         }
 #endif
@@ skipping 384 matching lines @@
 void AXObjectCache::handleScrolledToAnchor(const Node* anchorNode)
 {
     // The anchor node may not be accessible. Post the notification for the
     // first accessible object.
     postPlatformNotification(AccessibilityObject::firstAccessibleObjectFromNode(anchorNode), AXScrolledToAnchor);
 }
 
 } // namespace WebCore
 
 #endif // HAVE(ACCESSIBILITY)