Fix under-invalidation of frame scrollbar on hover

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 240 matching lines @@
 
     // GraphicsLayers for the scrolling components.
     //
     // Any function can return nullptr if they are not accelerated.
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
     GraphicsLayer* layerForScrollCorner() const override;
 
     bool usesCompositedScrolling() const override;
     bool shouldScrollOnMainThread() const override;
-    void scrollControlWasSetNeedsPaintInvalidation() override;
     bool shouldUseIntegerScrollOffset() const override;
     bool isActive() const override;
     bool isScrollCornerVisible() const override;
     IntRect scrollCornerRect() const override;
     IntRect convertFromScrollbarToContainingWidget(const Scrollbar&, const IntRect&) const override;
     IntRect convertFromContainingWidgetToScrollbar(const Scrollbar&, const IntRect&) const override;
     IntPoint convertFromScrollbarToContainingWidget(const Scrollbar&, const IntPoint&) const override;
     IntPoint convertFromContainingWidgetToScrollbar(const Scrollbar&, const IntPoint&) const override;
     int scrollSize(ScrollbarOrientation) const override;
     IntPoint scrollPosition() const override;
@@ skipping 272 matching lines @@
 #endif
 };
 
 DEFINE_TYPE_CASTS(PaintLayerScrollableArea, ScrollableArea, scrollableArea,
     scrollableArea->isPaintLayerScrollableArea(),
     scrollableArea.isPaintLayerScrollableArea());
 
 } // namespace blink
 
 #endif // LayerScrollableArea_h