Prefer to forward-declare GraphicsContext in headers.

Source/platform/mac/LocalCurrentGraphicsContext.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
-#include "platform/graphics/GraphicsContext.h"
+#include "platform/PlatformExport.h"
+#include "skia/ext/skia_utils_mac.h"
 #include "wtf/Noncopyable.h"
 
-#include "skia/ext/skia_utils_mac.h"
-
 OBJC_CLASS NSGraphicsContext;
 
 namespace WebCore {
 
+class GraphicsContext;
+
 // This class automatically saves and restores the current NSGraphicsContext for
 // functions which call out into AppKit and rely on the currentContext being set
 class PLATFORM_EXPORT LocalCurrentGraphicsContext {
     WTF_MAKE_NONCOPYABLE(LocalCurrentGraphicsContext);
 public:
     LocalCurrentGraphicsContext(GraphicsContext* graphicsContext);
     ~LocalCurrentGraphicsContext();
     CGContextRef cgContext();
 private:
     GraphicsContext* m_savedGraphicsContext;
     NSGraphicsContext* m_savedNSGraphicsContext;
     bool m_didSetGraphicsContext;
     gfx::SkiaBitLocker m_skiaBitLocker;
 };
 
 class PLATFORM_EXPORT ContextContainer {
     WTF_MAKE_NONCOPYABLE(ContextContainer);
 public:
     ContextContainer(GraphicsContext*);
 
     // This synchronizes the CGContext to reflect the current SkCanvas state.
     // The implementation may not return the same CGContext each time.
     CGContextRef context() { return m_skiaBitLocker.cgContext(); }
 
 private:
     gfx::SkiaBitLocker m_skiaBitLocker;
 };
 
 }