Move paint code for RenderScrollbar and RenderScrollbarPart into ScrollbarPainter.

Source/core/rendering/RenderScrollbarPart.h

Index: Source/core/rendering/RenderScrollbarPart.h
diff --git a/Source/core/rendering/RenderScrollbarPart.h b/Source/core/rendering/RenderScrollbarPart.h
index 7db24c6b716d3aa84f280e78917229a03ce882d5..b526ffc1b7ff61c07ab779d4373b7ae343e04904 100644
--- a/Source/core/rendering/RenderScrollbarPart.h
+++ b/Source/core/rendering/RenderScrollbarPart.h
@@ -45,8 +45,6 @@ public:
 
     virtual void layout() OVERRIDE;
 
-    void paintIntoRect(GraphicsContext*, const LayoutPoint&, const LayoutRect&);
-
     // Scrollbar parts needs to be rendered at device pixel boundaries.
     virtual LayoutUnit marginTop() const OVERRIDE { ASSERT(isIntegerValue(m_marginBox.top())); return m_marginBox.top(); }
     virtual LayoutUnit marginBottom() const OVERRIDE { ASSERT(isIntegerValue(m_marginBox.bottom())); return m_marginBox.bottom(); }