Take CSS Clip and contain: paint into account when computing visual rects.

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 563 matching lines @@
 
     m_owningLayer.update3DTransformedDescendantStatus();
     if (style.preserves3D() && style.hasOpacity() && m_owningLayer.has3DTransformedDescendant())
         UseCounter::count(layoutObject->document(), UseCounter::OpacityWithPreserve3DQuirk);
 
     return layerConfigChanged;
 }
 
 static IntRect clipBox(LayoutBox* layoutObject)
 {
-    LayoutRect result = LayoutRect(LayoutRect::infiniteIntRect());
-    if (layoutObject->hasOverflowClip() || layoutObject->style()->containsPaint())
-        result = layoutObject->overflowClipRect(LayoutPoint());
-
-    if (layoutObject->hasClip())
-        result.intersect(layoutObject->clipRect(LayoutPoint()));
-
-    return pixelSnappedIntRect(result);
+    // TODO(chrishtr): pixel snapping is most likely incorrect here.
+    return pixelSnappedIntRect(layoutObject->clippingRect());
 }
 
 static LayoutPoint computeOffsetFromCompositedAncestor(const PaintLayer* layer, const PaintLayer* compositedAncestor)
 {
     LayoutPoint offset = layer->visualOffsetFromAncestor(compositedAncestor);
     if (compositedAncestor)
         offset.move(compositedAncestor->compositedLayerMapping()->owningLayer().subpixelAccumulation());
     return offset;
 }
 
@@ skipping 2107 matching lines @@
     } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
         name = "Scrolling Contents Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink