Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXScrollView.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 19 matching lines @@
 
 namespace blink {
 
 class AXObjectCacheImpl;
 class AXScrollbar;
 class Scrollbar;
 class FrameView;
 
 class AXScrollView final : public AXObject {
 public:
-    static PassRefPtr<AXScrollView> create(FrameView*, AXObjectCacheImpl*);
+    static PassRefPtr<AXScrollView> create(FrameView*, AXObjectCacheImpl&);
     virtual AccessibilityRole roleValue() const override { return ScrollAreaRole; }
     FrameView* scrollView() const { return m_scrollView; }
 
     virtual ~AXScrollView();
     virtual void detach() override;
 
 protected:
     virtual ScrollableArea* getScrollableAreaIfScrollable() const override;
 
 private:
-    AXScrollView(FrameView*, AXObjectCacheImpl*);
+    AXScrollView(FrameView*, AXObjectCacheImpl&);
 
     virtual bool computeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const override;
     virtual bool isAXScrollView() const override { return true; }
     virtual bool isEnabled() const override { return true; }
 
     virtual bool isAttachment() const override;
     virtual Widget* widgetForAttachmentView() const override;
 
     virtual AXObject* scrollBar(AccessibilityOrientation) override;
     virtual void addChildren() override;
@@ skipping 27 matching lines @@
     RefPtr<AXObject> m_horizontalScrollbar;
     RefPtr<AXObject> m_verticalScrollbar;
     bool m_childrenDirty;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXScrollView, isAXScrollView());
 
 } // namespace blink
 
 #endif // AXScrollView_h