CSS clip property should not force additional clamping to border box

Source/core/rendering/RenderLayer.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@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 5011 matching lines @@
         // rect is intersected with our layer's bounds including our visual overflow,
         // since any visual overflow like box-shadow or border-outset is not clipped by overflow:auto/hidden.
         if (renderBox()->hasVisualOverflow()) {
             // FIXME: Does not do the right thing with CSS regions yet, since we don't yet factor in the
             // individual region boxes as overflow.
             LayoutRect layerBoundsWithVisualOverflow = renderBox()->visualOverflowRect();
             renderBox()->flipForWritingMode(layerBoundsWithVisualOverflow); // Layers are in physical coordinates, so the overflow has to be flipped.
             layerBoundsWithVisualOverflow.moveBy(offset);
             if (this != clipRectsContext.rootLayer || clipRectsContext.respectOverflowClip == RespectOverflowClip)
                 backgroundRect.intersect(layerBoundsWithVisualOverflow);
-        } else {
+        } else if (renderer()->hasOverflowClip()) {
             // Shift the bounds to be for our region only.
             LayoutRect bounds = renderBox()->borderBoxRectInRegion(clipRectsContext.region);
             bounds.moveBy(offset);
             if (this != clipRectsContext.rootLayer || clipRectsContext.respectOverflowClip == RespectOverflowClip)
                 backgroundRect.intersect(bounds);
         }
     }
 }
 
 LayoutRect RenderLayer::childrenClipRect() const
@@ skipping 1354 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif