Revert 146726 "AXObjectCache gets recreated during document tear..."

Source/WebCore/rendering/RenderListBox.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  *               2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * 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. 
@@ skipping 148 matching lines @@
 void RenderListBox::selectionChanged()
 {
     repaint();
     if (!m_inAutoscroll) {
         if (m_optionsChanged || needsLayout())
             m_scrollToRevealSelectionAfterLayout = true;
         else
             scrollToRevealSelection();
     }
     
-    if (AXObjectCache* cache = document()->existingAXObjectCache())
-        cache->selectedChildrenChanged(this);
+    if (AXObjectCache::accessibilityEnabled())
+        document()->axObjectCache()->selectedChildrenChanged(this);
 }
 
 void RenderListBox::layout()
 {
     StackStats::LayoutCheckPoint layoutCheckPoint;
     RenderBlock::layout();
 
     if (m_vBar) {
         bool enabled = numVisibleItems() < numItems();
         m_vBar->setEnabled(enabled);
@@ skipping 700 matching lines @@
         m_vBar->styleChanged();
 
     // Force an update since we know the scrollbars have changed things.
 #if ENABLE(DASHBOARD_SUPPORT) || ENABLE(DRAGGABLE_REGION)
     if (document()->hasAnnotatedRegions())
         document()->setAnnotatedRegionsDirty(true);
 #endif
 }
 
 } // namespace WebCore