Oilpan: Prepare to move form control ua shadow elements to Oilpan heap.

Source/core/html/shadow/ClearButtonElement.h

 /*
  * Copyright (C) 2013 Google 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 15 matching lines @@
 #ifndef ClearButtonElement_h
 #define ClearButtonElement_h
 
 #include "core/html/HTMLDivElement.h"
 #include "wtf/Forward.h"
 
 namespace WebCore {
 
 class ClearButtonElement FINAL : public HTMLDivElement {
 public:
-    class ClearButtonOwner {
+    class ClearButtonOwner : public WillBeGarbageCollectedMixin {
     public:
         virtual ~ClearButtonOwner() { }
         virtual void focusAndSelectClearButtonOwner() = 0;
         virtual bool shouldClearButtonRespondToMouseEvents() = 0;
         virtual void clearValue() = 0;
     };
 
-    static PassRefPtr<ClearButtonElement> create(Document&, ClearButtonOwner&);
+    static PassRefPtrWillBeRawPtr<ClearButtonElement> create(Document&, ClearButtonOwner&);
     void releaseCapture();
-    void removeClearButtonOwner() { m_clearButtonOwner = 0; }
+    void removeClearButtonOwner() { m_clearButtonOwner = nullptr; }
+
+    virtual void trace(Visitor*) OVERRIDE;
 
 private:
     ClearButtonElement(Document&, ClearButtonOwner&);
     virtual void detach(const AttachContext& = AttachContext()) OVERRIDE;
     virtual bool isMouseFocusable() const OVERRIDE { return false; }
     virtual void defaultEventHandler(Event*) OVERRIDE;
     virtual bool isClearButtonElement() const OVERRIDE;
 
-    ClearButtonOwner* m_clearButtonOwner;
+    RawPtrWillBeMember<ClearButtonOwner> m_clearButtonOwner;
     bool m_capturing;
 };
 
 DEFINE_TYPE_CASTS(ClearButtonElement, Element, element, element->isClearButtonElement(), element.isClearButtonElement());
 
 } // namespace
 
 #endif // ClearButtonElement_h