Move NinePieceImage painting to a separate class

Source/core/paint/NinePieceImagePainter.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 NinePieceImagePainter_h
+#define NinePieceImagePainter_h
+
+#include "platform/LayoutUnit.h"
+#include "platform/heap/Heap.h"
+#include "third_party/skia/include/core/SkXfermode.h"
+
+namespace blink {
+
+class ComputedStyle;
+class GraphicsContext;
+class LayoutBoxModelObject;
+class LayoutRect;
+class NinePieceImage;
+class BorderImageLength;
+
+class NinePieceImagePainter {
+    STACK_ALLOCATED();
+public:
+    NinePieceImagePainter(LayoutBoxModelObject&);
+
+    bool paint(GraphicsContext*, const LayoutRect&, const ComputedStyle&, const NinePieceImage&, SkXfermode::Mode) const;
+
+private:
+    static LayoutUnit computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit borderSide, LayoutUnit imageSide, LayoutUnit boxExtent);
+
+    LayoutBoxModelObject& m_layoutObject;
+};
+
+} // namespace blink
+
+#endif // NinePieceImagePainter_h