C++11: Replace 0 with nullptr where applicable in layout code.

Source/core/layout/svg/SVGMarkerData.h

 /*
  * Copyright (C) Research In Motion Limited 2010. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 73 matching lines @@
         switch (type) {
         case StartMarker:
             return markerStart;
         case MidMarker:
             return markerMid;
         case EndMarker:
             return markerEnd;
         }
 
         ASSERT_NOT_REACHED();
-        return 0;
+        return nullptr;
     }
 
 private:
     float currentAngle(SVGMarkerType type) const
     {
         // For details of this calculation, see: http://www.w3.org/TR/SVG/single-page.html#painting-MarkerElement
         FloatPoint inSlope(m_inslopePoints[1] - m_inslopePoints[0]);
         FloatPoint outSlope(m_outslopePoints[1] - m_outslopePoints[0]);
 
         double inAngle = rad2deg(inSlope.slopeAngleRadians());
@@ skipping 61 matching lines @@
     FloatPoint m_origin;
     FloatPoint m_subpathStart;
     FloatPoint m_inslopePoints[2];
     FloatPoint m_outslopePoints[2];
     bool m_autoStartReverse;
 };
 
 }
 
 #endif // SVGMarkerData_h