Move paint code for RenderScrollbar and RenderScrollbarPart into ScrollbarPainter.

Source/core/paint/ScrollbarPainter.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 ScrollbarPainter_h
+#define ScrollbarPainter_h
+
+#include "platform/scroll/Scrollbar.h"
+
+namespace blink {
+
+class GraphicsContext;
+struct PaintInfo;
+class IntRect;
+class LayoutPoint;
+class LayoutRect;
+class RenderScrollbar;
+class RenderScrollbarPart;
+
+class ScrollbarPainter {
+public:
+    ScrollbarPainter(RenderScrollbar& renderScrollbar) : m_renderScrollbar(renderScrollbar) { }
+
+    void paintPart(GraphicsContext*, ScrollbarPart, const IntRect&);
+    static void paintIntoRect(RenderScrollbarPart*, GraphicsContext*, const LayoutPoint& paintOffset, const LayoutRect&);
+
+private:
+    RenderScrollbar& m_renderScrollbar;
+};
+
+} // namespace blink
+
+#endif // ScrollbarPainter_h