Detach PaintLayerScrollableArea from RootFrameViewport when disposed.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.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 29 matching lines @@
  * If you do not delete the provisions above, a recipient may use your
  * version of this file under any of the LGPL, the MPL or the GPL.
  */
 
 #ifndef PaintLayerScrollableArea_h
 #define PaintLayerScrollableArea_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ScrollAnchor.h"
 #include "core/layout/ScrollEnums.h"
+#include "core/page/scrolling/StickyPositionScrollingConstraints.h"
 #include "core/paint/PaintInvalidationCapableScrollableArea.h"
 #include "core/paint/PaintLayerFragment.h"
 #include "platform/heap/Handle.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
 
 namespace blink {
 
 enum ResizerHitTestType {
     ResizerForPointer,
@@ skipping 485 matching lines @@
 #endif
 };
 
 DEFINE_TYPE_CASTS(PaintLayerScrollableArea, ScrollableArea, scrollableArea,
     scrollableArea->isPaintLayerScrollableArea(),
     scrollableArea.isPaintLayerScrollableArea());
 
 } // namespace blink
 
 #endif // LayerScrollableArea_h