Prefer to forward-declare GraphicsContext in headers.

Source/core/fetch/ImageResource.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 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 16 matching lines @@
 #include "RuntimeEnabledFeatures.h"
 #include "core/fetch/ImageResourceClient.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/fetch/ResourceClient.h"
 #include "core/fetch/ResourceClientWalker.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/FrameView.h"
 #include "core/rendering/RenderObject.h"
 #include "core/svg/graphics/SVGImage.h"
 #include "platform/SharedBuffer.h"
+#include "platform/TraceEvent.h"
 #include "platform/graphics/BitmapImage.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/Vector.h"
 
 namespace WebCore {
 
 ImageResource::ImageResource(const ResourceRequest& resourceRequest)
     : Resource(resourceRequest, Image)
     , m_devicePixelRatioHeaderValue(1.0)
@@ skipping 420 matching lines @@
 bool ImageResource::isAccessAllowed(SecurityOrigin* securityOrigin)
 {
     if (!image()->currentFrameHasSingleSecurityOrigin())
         return false;
     if (passesAccessControlCheck(securityOrigin))
         return true;
     return !securityOrigin->taintsCanvas(response().url());
 }
 
 } // namespace WebCore