Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXMockObject.cpp

 /*
  * Copyright (C) 2011 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 12 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "modules/accessibility/AXMockObject.h"
 
 #include "modules/accessibility/AXObjectCacheImpl.h"
 
 namespace blink {
 
-AXMockObject::AXMockObject(AXObjectCacheImpl* axObjectCache)
+AXMockObject::AXMockObject(AXObjectCacheImpl& axObjectCache)
     : AXObject(axObjectCache)
 {
 }
 
 AXMockObject::~AXMockObject()
 {
 }
 
 bool AXMockObject::computeAccessibilityIsIgnored(IgnoredReasons* ignoredReasons) const
 {
     return accessibilityIsIgnoredByDefault(ignoredReasons);
 }
 
 }