[S.P.] Move svg mask painting to SVGMaskPainter

Source/core/paint/SVGMaskPainter.h

+// Copyright 2015 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 SVGMaskPainter_h
+#define SVGMaskPainter_h
+
+#include "platform/geometry/FloatRect.h"
+#include "platform/graphics/paint/DisplayItem.h"
+
+namespace blink {
+
+class GraphicsContext;
+class LayoutObject;
+class LayoutSVGResourceMasker;
+
+class SVGMaskPainter {
+public:
+    SVGMaskPainter(LayoutSVGResourceMasker& mask) : m_mask(mask) { }
+
+    bool prepareEffect(LayoutObject*, GraphicsContext*);
+    void finishEffect(LayoutObject*, GraphicsContext*);
+
+private:
+    void drawMaskForRenderer(GraphicsContext*, DisplayItemClient, const FloatRect& targetBoundingBox);
+
+    LayoutSVGResourceMasker& m_mask;
+};
+
+} // namespace blink
+
+#endif // SVGShapePainter_h