[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/page/DragController.h

 /*
  * Copyright (C) 2007, 2009 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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
  */
 
 #ifndef DragController_h
 #define DragController_h
 
 #include "core/page/DragActions.h"
 #include "core/platform/DragImage.h"
 #include "core/platform/KURL.h"
 #include "core/platform/graphics/IntPoint.h"
+#include "heap/Handle.h"
 
 namespace WebCore {
 
     class Clipboard;
     class Document;
     class DragClient;
     class DragData;
     struct DragSession;
     struct DragState;
     class Element;
@@ skipping 70 matching lines @@
         bool doDrag(Frame* src, Clipboard* clipboard, DragImageRef dragImage, const KURL& linkURL, const KURL& imageURL, Node* node, IntPoint& dragLoc, IntPoint& dragImageOffset);
         void doImageDrag(Element*, const IntPoint&, const IntRect&, Clipboard*, Frame*, IntPoint&);
         void doSystemDrag(DragImageRef, const IntPoint&, const IntPoint&, Clipboard*, Frame*, bool forLink);
         void cleanupAfterSystemDrag();
 
         Page* m_page;
         DragClient* m_client;
 
         RefPtr<Document> m_documentUnderMouse; // The document the mouse was last dragged over.
         RefPtr<Document> m_dragInitiator; // The Document (if any) that initiated the drag.
-        RefPtr<HTMLInputElement> m_fileInputElementUnderMouse;
+        Persistent<HTMLInputElement> m_fileInputElementUnderMouse;
         bool m_documentIsHandlingDrag;
 
         DragDestinationAction m_dragDestinationAction;
         DragSourceAction m_dragSourceAction;
         bool m_didInitiateDrag;
         DragOperation m_sourceDragOperation; // Set in startDrag when a drag starts from a mouse down within WebKit
         IntPoint m_dragOffset;
         KURL m_draggingImageURL;
     };
 
 }
 
 #endif