Fix the overflow clip rect rounding for overflow scrolling

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1216 matching lines @@
 }
 
 void CompositedLayerMapping::updateScrollingLayerGeometry(
     const IntRect& localCompositingBounds) {
   if (!m_scrollingLayer)
     return;
 
   ASSERT(m_scrollingContentsLayer);
   LayoutBox* layoutBox = toLayoutBox(layoutObject());
   IntRect overflowClipRect =
-      enclosingIntRect(layoutBox->overflowClipRect(LayoutPoint()));
+      pixelSnappedIntRect(layoutBox->overflowClipRect(LayoutPoint()));
   FloatPoint scrollPosition =
       m_owningLayer.getScrollableArea()->scrollPosition();
   m_scrollingLayer->setPosition(FloatPoint(
       overflowClipRect.location() - localCompositingBounds.location() +
       roundedIntSize(m_owningLayer.subpixelAccumulation())));
   m_scrollingLayer->setSize(FloatSize(overflowClipRect.size()));
 
   IntSize oldScrollingLayerOffset = m_scrollingLayer->offsetFromLayoutObject();
   m_scrollingLayer->setOffsetFromLayoutObject(
       -toIntSize(overflowClipRect.location()));
@@ skipping 2001 matching lines @@
   } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
     name = "Scrolling Contents Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink