Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXMockObject.h

 /*
  * 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 18 matching lines @@
 #include "modules/ModulesExport.h"
 #include "modules/accessibility/AXObject.h"
 
 namespace blink {
 
 class AXObjectCacheImpl;
 
 class MODULES_EXPORT AXMockObject : public AXObject {
 
 protected:
-    explicit AXMockObject(AXObjectCacheImpl*);
+    explicit AXMockObject(AXObjectCacheImpl&);
 
 public:
     virtual ~AXMockObject();
 
     // AXObject overrides.
     virtual AXObject* computeParent() const override { return m_parent; }
     virtual bool isEnabled() const override { return true; }
 
 private:
     virtual bool isMockObject() const override final { return true; }
 
     virtual bool computeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const override;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXMockObject, isMockObject());
 
 } // namespace blink
 
 #endif // AXMockObject_h