Optimize scroll adjustment for paint invalidation

third_party/WebKit/Source/core/layout/LayoutBoxModelObject.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 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. 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 1456 matching lines @@
     rootElementStyle = rootElement->ensureComputedStyle();
   if (rootElementStyle->hasBackground())
     return false;
 
   if (node() != document().firstBodyElement())
     return false;
 
   return true;
 }
 
+IntSize LayoutBoxModelObject::scrollAdjustmentForPaintInvalidation() const {
+  if (!hasOverflowClip() || usesCompositedScrolling())
+    return IntSize();
+  return -toLayoutBox(this)->scrolledContentOffset();
+}
+
 }  // namespace blink