Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXTableHeaderContainer.cpp

 /*
  * Copyright (C) 2008 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 15 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "modules/accessibility/AXTableHeaderContainer.h"
 
 #include "modules/accessibility/AXObjectCacheImpl.h"
 
 namespace blink {
 
-AXTableHeaderContainer::AXTableHeaderContainer(AXObjectCacheImpl* axObjectCache)
+AXTableHeaderContainer::AXTableHeaderContainer(AXObjectCacheImpl& axObjectCache)
     : AXMockObject(axObjectCache)
 {
 }
 
 AXTableHeaderContainer::~AXTableHeaderContainer()
 {
 }
 
-PassRefPtr<AXTableHeaderContainer> AXTableHeaderContainer::create(AXObjectCacheImpl* axObjectCache)
+PassRefPtr<AXTableHeaderContainer> AXTableHeaderContainer::create(AXObjectCacheImpl& axObjectCache)
 {
     return adoptRef(new AXTableHeaderContainer(axObjectCache));
 }
 
 LayoutRect AXTableHeaderContainer::elementRect() const
 {
     // this will be filled in when addChildren is called
     return m_headerRect;
 }
 
@@ skipping 20 matching lines @@
         return;
 
     toAXTable(m_parent)->columnHeaders(m_children);
 
     unsigned length = m_children.size();
     for (unsigned k = 0; k < length; ++k)
         m_headerRect.unite(m_children[k]->elementRect());
 }
 
 } // namespace blink