Fix the overflow clip rect rounding for overflow scrolling

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 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@gmail.com>
@@ skipping 461 matching lines @@
 }
 
 IntSize PaintLayerScrollableArea::minimumScrollOffsetInt() const {
   return toIntSize(-scrollOrigin());
 }
 
 IntSize PaintLayerScrollableArea::maximumScrollOffsetInt() const {
   IntSize contentSize;
   IntSize visibleSize;
   if (box().hasOverflowClip()) {
-    contentSize =
-        IntSize(pixelSnappedScrollWidth(), pixelSnappedScrollHeight());
+    contentSize = contentsSize();
     visibleSize =
         pixelSnappedIntRect(box().overflowClipRect(box().location())).size();
 
     // TODO(skobes): We should really ASSERT that contentSize >= visibleSize
     // when we are not the root layer, but we can't because contentSize is
     // based on stale layout overflow data (http://crbug.com/576933).
     contentSize = contentSize.expandedTo(visibleSize);
   }
   return toIntSize(-scrollOrigin() + (contentSize - visibleSize));
 }
@@ skipping 1471 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetsAfterLayout();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink