Plumb border radius through when computing clip visual rects.

third_party/WebKit/Source/core/paint/PaintLayerClipper.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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>
@@ skipping 212 matching lines @@
                                         LayoutRect&) const;
   // Same as calculateRects, but using GeometryMapper.
   void calculateRectsWithGeometryMapper(
       const ClipRectsContext&,
       const LayoutRect& paintDirtyRect,
       LayoutRect& layerBounds,
       ClipRect& backgroundRect,
       ClipRect& foregroundRect,
       const LayoutPoint* offsetFromRoot = 0) const;
 
-  ClipRect applyOverflowClipToBackgroundRectWithGeometryMapper(
+  void applyOverflowClipToBackgroundRectWithGeometryMapper(
       const ClipRectsContext&,
-      const ClipRect&) const;
+      ClipRect&) const;
 
   const PaintLayer& m_layer;
   std::unique_ptr<GeometryMapper> m_geometryMapper;
 
   friend class PaintLayerClipperTest;
 };
 
 }  // namespace blink
 
 #endif  // LayerClipper_h