Scaling and offset fix for FELighting (software and skia paths)

Source/platform/graphics/filters/DistantLightSource.h

 /*
  * Copyright (C) 2008 Alex Mathews <possessedpenguinbob@gmail.com>
  * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
  *
  * 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.
@@ skipping 22 matching lines @@
     {
         return adoptRef(new DistantLightSource(azimuth, elevation));
     }
 
     float azimuth() const { return m_azimuth; }
     float elevation() const { return m_elevation; }
 
     virtual bool setAzimuth(float) OVERRIDE;
     virtual bool setElevation(float) OVERRIDE;
 
-    virtual void initPaintingData(PaintingData&) OVERRIDE;
-    virtual void updatePaintingData(PaintingData&, int x, int y, float z) OVERRIDE;
+    virtual void initPaintingData(PaintingData&) const OVERRIDE;
+    virtual void updatePaintingData(PaintingData&, int x, int y, float z) const OVERRIDE;
 
     virtual TextStream& externalRepresentation(TextStream&) const OVERRIDE;
 
 private:
     DistantLightSource(float azimuth, float elevation)
         : LightSource(LS_DISTANT)
         , m_azimuth(azimuth)
         , m_elevation(elevation)
     {
     }
 
     float m_azimuth;
     float m_elevation;
 };
 
 } // namespace WebCore
 
 #endif // DistantLightSource_h