Oilpan: Prepare to move RenderObject and RenderObjectChildList to Oilpan heap.

Source/core/rendering/RenderLayerScrollableArea.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 231 matching lines @@
     // This is the (scroll) offset from scrollOrigin().
     IntSize m_scrollOffset;
 
     IntPoint m_cachedOverlayScrollbarOffset;
 
     // For areas with overflow, we have a pair of scrollbars.
     RefPtr<Scrollbar> m_hBar;
     RefPtr<Scrollbar> m_vBar;
 
     // Renderers to hold our custom scroll corner.
-    RenderScrollbarPart* m_scrollCorner;
+    RawPtrWillBePersistent<RenderScrollbarPart> m_scrollCorner;
 
     // Renderers to hold our custom resizer.
-    RenderScrollbarPart* m_resizer;
+    RawPtrWillBePersistent<RenderScrollbarPart> m_resizer;
 };
 
 } // namespace blink
 
 #endif // RenderLayerScrollableArea_h