LayoutView's paint layer should clip to the full viewport size.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 289 matching lines @@
   // In normal compositing mode, LayoutView doesn't actually apply clipping
   // on its descendants. Instead their visual overflow is propagated to
   // compositor()->m_rootContentLayer for accelerated scrolling.
   return layoutOverflowRect();
 }
 
 LayoutRect LayoutView::localVisualRect() const {
   // TODO(wangxianzhu): This is only required without rootLayerScrolls (though
   // it is also correct but unnecessary with rootLayerScrolls) because of the
   // special LayoutView overflow model.
-  return visualOverflowRect();
+  LayoutRect rect = visualOverflowRect();
+  rect.unite(LayoutRect(rect.location(), viewRect().size()));
+  return rect;
 }
 
 void LayoutView::mapLocalToAncestor(const LayoutBoxModelObject* ancestor,
                                     TransformState& transformState,
                                     MapCoordinatesFlags mode) const {
   if (!ancestor && mode & UseTransforms && shouldUseTransformFromContainer(0)) {
     TransformationMatrix t;
     getTransformFromContainer(0, LayoutSize(), t);
     transformState.applyTransform(t);
   }
@@ skipping 717 matching lines @@
   if (block)
     block->adjustChildDebugRect(rect);
 
   rect.setWidth(LayoutUnit(viewWidth(IncludeScrollbars)));
   rect.setHeight(LayoutUnit(viewHeight(IncludeScrollbars)));
 
   return rect;
 }
 
 }  // namespace blink