Oilpan: improve ScrollableArea handling.

Source/core/paint/DeprecatedPaintLayerScrollableArea.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 DeprecatedPaintLayerScrollableArea_h
 #define DeprecatedPaintLayerScrollableArea_h
 
 #include "core/CoreExport.h"
 #include "core/layout/LayoutBox.h"
 #include "core/paint/DeprecatedPaintLayerFragment.h"
+#include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollableArea.h"
 
 namespace blink {
 
 enum ResizerHitTestType {
     ResizerForPointer,
     ResizerForTouch
 };
 
 class PlatformEvent;
 class LayoutBox;
 class DeprecatedPaintLayer;
 class LayoutScrollbarPart;
 
-class CORE_EXPORT DeprecatedPaintLayerScrollableArea final : public ScrollableArea {
+class CORE_EXPORT DeprecatedPaintLayerScrollableArea final : public NoBaseWillBeGarbageCollectedFinalized<DeprecatedPaintLayerScrollableArea>, public ScrollableArea {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(DeprecatedPaintLayerScrollableArea);
     friend class Internals;
 
 public:
     // FIXME: We should pass in the LayoutBox but this opens a window
     // for crashers during DeprecatedPaintLayer setup (see crbug.com/368062).
-    DeprecatedPaintLayerScrollableArea(DeprecatedPaintLayer&);
+    static PassOwnPtrWillBeRawPtr<DeprecatedPaintLayerScrollableArea> create(DeprecatedPaintLayer& layer)
+    {
+        return adoptPtrWillBeNoop(new DeprecatedPaintLayerScrollableArea(layer));
+    }
+
     virtual ~DeprecatedPaintLayerScrollableArea();
+    void dispose();
 
     bool hasHorizontalScrollbar() const { return horizontalScrollbar(); }
     bool hasVerticalScrollbar() const { return verticalScrollbar(); }
 
     virtual Scrollbar* horizontalScrollbar() const override { return m_hBar.get(); }
     virtual Scrollbar* verticalScrollbar() const override { return m_vBar.get(); }
 
     virtual HostWindow* hostWindow() const override;
 
     virtual GraphicsLayer* layerForScrolling() const override;
@@ skipping 126 matching lines @@
     DeprecatedPaintLayer* layer() const;
 
     LayoutScrollbarPart* resizer() { return m_resizer; }
 
     const IntPoint& cachedOverlayScrollbarOffset() { return m_cachedOverlayScrollbarOffset; }
     void setCachedOverlayScrollbarOffset(const IntPoint& offset) { m_cachedOverlayScrollbarOffset = offset; }
 
     IntRect rectForHorizontalScrollbar(const IntRect& borderBoxRect) const;
     IntRect rectForVerticalScrollbar(const IntRect& borderBoxRect) const;
 
+    DECLARE_VIRTUAL_TRACE();
+
 private:
+    explicit DeprecatedPaintLayerScrollableArea(DeprecatedPaintLayer&);
+
     bool hasHorizontalOverflow() const;
     bool hasVerticalOverflow() const;
     bool hasScrollableHorizontalOverflow() const;
     bool hasScrollableVerticalOverflow() const;
 
     void computeScrollDimensions();
 
     // TODO(bokan): This method hides the base class version and is subtly different.
     // Should be unified.
     DoubleSize clampScrollOffset(const DoubleSize&) const;
@@ skipping 40 matching lines @@
 
     // The width/height of our scrolled area.
     LayoutRect m_overflowRect;
 
     // This is the (scroll) offset from scrollOrigin().
     DoubleSize m_scrollOffset;
 
     IntPoint m_cachedOverlayScrollbarOffset;
 
     // For areas with overflow, we have a pair of scrollbars.
-    RefPtrWillBePersistent<Scrollbar> m_hBar;
-    RefPtrWillBePersistent<Scrollbar> m_vBar;
+    RefPtrWillBeMember<Scrollbar> m_hBar;
+    RefPtrWillBeMember<Scrollbar> m_vBar;
 
     // LayoutObject to hold our custom scroll corner.
     LayoutScrollbarPart* m_scrollCorner;
 
     // LayoutObject to hold our custom resizer.
     LayoutScrollbarPart* m_resizer;
+
+#if ENABLE(ASSERT)
+    bool m_hasBeenDisposed;
+#endif
 };
 
 } // namespace blink
 
 #endif // LayerScrollableArea_h