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

Source/platform/graphics/filters/LightSource.h

Index: Source/platform/graphics/filters/LightSource.h
diff --git a/Source/platform/graphics/filters/LightSource.h b/Source/platform/graphics/filters/LightSource.h
index 255f66935b1b6aa28395494c9a2e1e2872a7b1bd..4c7d412a862642649fb9144f5d043dabcca449b9 100644
--- a/Source/platform/graphics/filters/LightSource.h
+++ b/Source/platform/graphics/filters/LightSource.h
@@ -69,10 +69,12 @@ public:
     LightType type() const { return m_type; }
     virtual TextStream& externalRepresentation(TextStream&) const = 0;
 
-    virtual void initPaintingData(PaintingData&) = 0;
+    virtual PassRefPtr<LightSource> create(const FloatPoint3D& scale, const FloatSize& offset) const = 0;
+
+    virtual void initPaintingData(PaintingData&) const = 0;
     // z is a float number, since it is the alpha value scaled by a user
     // specified "surfaceScale" constant, which type is <number> in the SVG standard
-    virtual void updatePaintingData(PaintingData&, int x, int y, float z) = 0;
+    virtual void updatePaintingData(PaintingData&, int x, int y, float z) const = 0;
 
     virtual bool setAzimuth(float) { return false; }
     virtual bool setElevation(float) { return false; }