Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXListBoxOption.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 21 matching lines @@
 #include "core/html/HTMLOptionElement.h"
 #include "core/html/HTMLSelectElement.h"
 #include "core/layout/LayoutListBox.h"
 #include "modules/accessibility/AXObjectCacheImpl.h"
 
 
 namespace blink {
 
 using namespace HTMLNames;
 
-AXListBoxOption::AXListBoxOption(LayoutObject* layoutObject, AXObjectCacheImpl* axObjectCache)
+AXListBoxOption::AXListBoxOption(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
     : AXLayoutObject(layoutObject, axObjectCache)
 {
 }
 
 AXListBoxOption::~AXListBoxOption()
 {
 }
 
-PassRefPtr<AXListBoxOption> AXListBoxOption::create(LayoutObject* layoutObject, AXObjectCacheImpl* axObjectCache)
+PassRefPtr<AXListBoxOption> AXListBoxOption::create(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
 {
     return adoptRef(new AXListBoxOption(layoutObject, axObjectCache));
 }
 
 AccessibilityRole AXListBoxOption::determineAccessibilityRole()
 {
     if ((m_ariaRole = determineAriaRoleAttribute()) != UnknownRole)
         return m_ariaRole;
 
     // http://www.w3.org/TR/wai-aria/complete#presentation
@@ skipping 130 matching lines @@
     unsigned length = listItems.size();
     for (unsigned i = 0; i < length; i++) {
         if (listItems[i] == node())
             return i;
     }
 
     return -1;
 }
 
 } // namespace blink