Prefer to forward-declare GraphicsContext in headers.

Source/core/fetch/Resource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
 
     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
@@ skipping 18 matching lines @@
 #include "core/fetch/CrossOriginAccessControl.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/fetch/ResourceClient.h"
 #include "core/fetch/ResourceClientWalker.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/fetch/ResourceLoader.h"
 #include "core/fetch/ResourcePtr.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "platform/Logging.h"
 #include "platform/SharedBuffer.h"
+#include "platform/TraceEvent.h"
 #include "platform/weborigin/KURL.h"
 #include "public/platform/Platform.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/MathExtras.h"
 #include "wtf/RefCountedLeakCounter.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/Vector.h"
 #include "wtf/text/CString.h"
 
 using namespace WTF;
@@ skipping 940 matching lines @@
         return "ImportResource";
     case Resource::Media:
         return "Media";
     }
     ASSERT_NOT_REACHED();
     return "Unknown";
 }
 #endif // !LOG_DISABLED
 
 }