Revert of Revert "Disable local background equivalence when we have a box shadow due to painting bug

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 111 matching lines @@
          scrollableArea->verticalScrollbar()->isCustomScrollbar())) {
       hasCustomScrollbars = true;
     }
   }
 
   // TODO(flackr): When we correctly clip the scrolling contents layer we can
   // paint locally equivalent backgrounds into it. https://crbug.com/645957
   if (!style()->hasAutoClip())
     return BackgroundPaintInGraphicsLayer;
 
+  // TODO(flackr): Remove this when box shadows are still painted correctly when
+  // painting into the composited scrolling contents layer.
+  // https://crbug.com/646464
+  if (style()->boxShadow())
+    return BackgroundPaintInGraphicsLayer;
+
   // Assume optimistically that the background can be painted in the scrolling
   // contents until we find otherwise.
   BackgroundPaintLocation paintLocation = BackgroundPaintInScrollingContents;
   const FillLayer* layer = &(style()->backgroundLayers());
   for (; layer; layer = layer->next()) {
     if (layer->attachment() == LocalBackgroundAttachment)
       continue;
 
     // Solid color layers with an effective background clip of the padding box
     // can be treated as local.
@@ skipping 1179 matching lines @@
   if (rootElementStyle->hasBackground())
     return false;
 
   if (node() != document().firstBodyElement())
     return false;
 
   return true;
 }
 
 }  // namespace blink