Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXMenuListOption.h

 /*
  * Copyright (C) 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "core/html/HTMLOptionElement.h"
 #include "modules/accessibility/AXMockObject.h"
 
 namespace blink {
 
 class AXObjectCacheImpl;
 
 class AXMenuListOption final : public AXMockObject {
 public:
-    static PassRefPtr<AXMenuListOption> create(HTMLOptionElement* element, AXObjectCacheImpl* axObjectCache) { return adoptRef(new AXMenuListOption(element, axObjectCache)); }
+    static PassRefPtr<AXMenuListOption> create(HTMLOptionElement* element, AXObjectCacheImpl& axObjectCache) { return adoptRef(new AXMenuListOption(element, axObjectCache)); }
 
 private:
-    explicit AXMenuListOption(HTMLOptionElement*, AXObjectCacheImpl*);
+    explicit AXMenuListOption(HTMLOptionElement*, AXObjectCacheImpl&);
 
     virtual bool isMenuListOption() const override { return true; }
 
     virtual Node* node() const override { return m_element; }
     virtual void detach() override;
     virtual bool isDetached() const override { return !m_element; }
     virtual AccessibilityRole roleValue() const override { return MenuListOptionRole; }
     virtual bool canHaveChildren() const override { return false; }
 
     virtual Element* actionElement() const override;
     virtual bool isEnabled() const override;
     virtual bool isVisible() const override;
     virtual bool isOffScreen() const override;
     virtual bool isSelected() const override;
     virtual void setSelected(bool) override;
     virtual bool canSetSelectedAttribute() const override;
     virtual LayoutRect elementRect() const override;
     virtual String stringValue() const override;
     virtual bool computeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const override;
 
     HTMLOptionElement* m_element;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXMenuListOption, isMenuListOption());
 
 } // namespace blink
 
 #endif // AXMenuListOption_h