Prefer to forward-declare GraphicsContext in headers.

Source/platform/scroll/ScrollbarThemeOverlay.h

 /*
  * Copyright (C) 2011 Google 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
  *     documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ScrollbarThemeOverlay_h
 #define ScrollbarThemeOverlay_h
 
+#include "platform/graphics/Color.h"
 #include "platform/scroll/ScrollbarTheme.h"
 
 namespace WebCore {
 
 // This scrollbar theme is used to get overlay scrollbar for platforms other
 // than Mac. Mac's overlay scrollbars are in ScrollbarThemeMac*.
 class PLATFORM_EXPORT ScrollbarThemeOverlay : public ScrollbarTheme {
 public:
     enum HitTestBehavior { AllowHitTest, DisallowHitTest };
 
@@ skipping 22 matching lines @@
     int m_thumbThickness;
     int m_scrollbarMargin;
     HitTestBehavior m_allowHitTest;
     Color m_color;
     const bool m_useSolidColor;
 };
 
 } // namespace WebCore
 
 #endif