Remove unnecessary dependency upon ScrollView from the ScrollbarTheme classes.

Source/core/rendering/RenderScrollbarTheme.h

Index: Source/core/rendering/RenderScrollbarTheme.h
diff --git a/Source/core/rendering/RenderScrollbarTheme.h b/Source/core/rendering/RenderScrollbarTheme.h
index 8da44cdd0fbbdf1721baafc6a418bebdb0039f8d..eed348943d13f4aae2cab0bf27a82af85729d5a9 100644
--- a/Source/core/rendering/RenderScrollbarTheme.h
+++ b/Source/core/rendering/RenderScrollbarTheme.h
@@ -32,7 +32,6 @@ namespace WebCore {
 
 class PlatformMouseEvent;
 class Scrollbar;
-class ScrollView;
 
 class RenderScrollbarTheme : public ScrollbarTheme {
 public:
@@ -44,7 +43,7 @@ public:
 
     virtual bool supportsControlTints() const OVERRIDE { return true; }
 
-    virtual void paintScrollCorner(ScrollView*, GraphicsContext*, const IntRect& cornerRect) OVERRIDE;
+    virtual void paintScrollCorner(GraphicsContext*, const IntRect& cornerRect) OVERRIDE;
 
     virtual bool shouldCenterOnThumb(ScrollbarThemeClient* scrollbar, const PlatformMouseEvent& event) OVERRIDE { return ScrollbarTheme::theme()->shouldCenterOnThumb(scrollbar, event); }