Move <svg:image> buffered-rendering management to SVGImagePainter

Source/core/paint/SVGImagePainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SVGImagePainter_h
 #define SVGImagePainter_h
 
 namespace blink {
 
+class AffineTransform;
+class FloatRect;
+class ImageBuffer;
+class IntSize;
 struct PaintInfo;
 class RenderSVGImage;
 
 class SVGImagePainter {
 public:
     SVGImagePainter(RenderSVGImage& renderSVGImage) : m_renderSVGImage(renderSVGImage) { }
 
     void paint(PaintInfo&);
 
+private:
+    bool bufferForeground(PaintInfo&);
     // Assumes the PaintInfo context has had all local transforms applied.
-    static void paintForeground(RenderSVGImage&, PaintInfo&);
+    void paintForeground(PaintInfo&);
 
-private:
     RenderSVGImage& m_renderSVGImage;
 };
 
 } // namespace blink
 
 #endif // SVGImagePainter_h