Prefer to forward-declare GraphicsContext in headers.

Source/web/WebDevToolsAgentImpl.cpp

 /*
  * Copyright (C) 2010-2011 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 30 matching lines @@
 #include "core/fetch/MemoryCache.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/inspector/InjectedScriptHost.h"
 #include "core/inspector/InspectorController.h"
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/rendering/RenderView.h"
 #include "platform/JSONValues.h"
+#include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/network/ResourceError.h"
 #include "platform/network/ResourceRequest.h"
 #include "platform/network/ResourceResponse.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebRect.h"
 #include "public/platform/WebString.h"
 #include "public/platform/WebURL.h"
 #include "public/platform/WebURLError.h"
 #include "public/platform/WebURLRequest.h"
@@ skipping 660 matching lines @@
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_removeBreakpointCmd)
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_setBreakpointsActiveCmd);
 }
 
 void WebDevToolsAgent::processPendingMessages()
 {
     PageScriptDebugServer::shared().runPendingTasks();
 }
 
 } // namespace blink