Prefer to forward-declare GraphicsContext in headers.

Source/core/rendering/RenderScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 
 #include "config.h"
 #include "core/rendering/RenderScrollbar.h"
 
 #include "core/css/PseudoStyleRequest.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/rendering/RenderPart.h"
 #include "core/rendering/RenderScrollbarPart.h"
 #include "core/rendering/RenderScrollbarTheme.h"
+#include "platform/graphics/GraphicsContext.h"
 
 namespace WebCore {
 
 PassRefPtr<Scrollbar> RenderScrollbar::createCustomScrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, Node* ownerNode, LocalFrame* owningFrame)
 {
     return adoptRef(new RenderScrollbar(scrollableArea, orientation, ownerNode, owningFrame));
 }
 
 RenderScrollbar::RenderScrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, Node* ownerNode, LocalFrame* owningFrame)
     : Scrollbar(scrollableArea, orientation, RegularScrollbar, RenderScrollbarTheme::renderScrollbarTheme())
@@ skipping 305 matching lines @@
 int RenderScrollbar::minimumThumbLength()
 {
     RenderScrollbarPart* partRenderer = m_parts.get(ThumbPart);
     if (!partRenderer)
         return 0;
     partRenderer->layout();
     return orientation() == HorizontalScrollbar ? partRenderer->width() : partRenderer->height();
 }
 
 }