Clean up forward declarations in core/rendering and core/painting

Source/core/rendering/svg/RenderSVGResourceGradient.h

 /*
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * 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.
  *
@@ skipping 20 matching lines @@
 
 namespace blink {
 
 struct GradientData {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     RefPtr<Gradient> gradient;
     AffineTransform userspaceTransform;
 };
 
-class GraphicsContext;
-
 class RenderSVGResourceGradient : public RenderSVGResourcePaintServer {
 public:
     explicit RenderSVGResourceGradient(SVGGradientElement*);
 
     virtual void removeAllClientsFromCache(bool markForInvalidation = true) override final;
     virtual void removeClientFromCache(RenderObject*, bool markForInvalidation = true) override final;
 
     virtual SVGPaintServer preparePaintServer(const RenderObject&) override final;
 
     virtual bool isChildAllowed(RenderObject* child, RenderStyle*) const override final;
 
 protected:
     void addStops(GradientData*, const Vector<Gradient::ColorStop>&) const;
 
     virtual SVGUnitTypes::SVGUnitType gradientUnits() const = 0;
     virtual void calculateGradientTransform(AffineTransform&) = 0;
     virtual bool collectGradientAttributes(SVGGradientElement*) = 0;
     virtual void buildGradient(GradientData*) const = 0;
 
     GradientSpreadMethod platformSpreadMethodFromSVGType(SVGSpreadMethodType) const;
 
 private:
     bool m_shouldCollectGradientAttributes : 1;
     HashMap<const RenderObject*, OwnPtr<GradientData> > m_gradientMap;
 };
 
 }
 
 #endif