Fix several corner case issues of scrollbar paint invalidation

third_party/WebKit/Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 4827 matching lines @@
 
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender() && borderImage->isLoaded();
 }
 
 ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const
 {
     return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this) : nullptr;
 }
 
+void LayoutBox::clearPreviousPaintInvalidationRects()
+{
+    LayoutBoxModelObject::clearPreviousPaintInvalidationRects();
+    if (PaintLayerScrollableArea* scrollableArea = this->scrollableArea())
+        scrollableArea->clearPreviousPaintInvalidationRects();
+}
+
 } // namespace blink