Prefer to forward-declare GraphicsContext in headers.

Source/web/WebPagePopupImpl.cpp

 /*
  * Copyright (C) 2012 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 25 matching lines @@
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/loader/EmptyClients.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/page/Chrome.h"
 #include "core/page/DOMWindowPagePopup.h"
 #include "core/page/EventHandler.h"
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/page/PagePopupClient.h"
+#include "platform/TraceEvent.h"
 #include "public/platform/WebCursorInfo.h"
 #include "public/web/WebViewClient.h"
 #include "public/web/WebWidgetClient.h"
 #include "web/WebInputEventConversion.h"
 #include "web/WebSettingsImpl.h"
 #include "web/WebViewImpl.h"
 
 using namespace WebCore;
 using namespace std;
 
@@ skipping 346 matching lines @@
     // A WebPagePopupImpl instance usually has two references.
     //  - One owned by the instance itself. It represents the visible widget.
     //  - One owned by a WebViewImpl. It's released when the WebViewImpl ask the
     //    WebPagePopupImpl to close.
     // We need them because the closing operation is asynchronous and the widget
     // can be closed while the WebViewImpl is unaware of it.
     return adoptRef(new WebPagePopupImpl(client)).leakRef();
 }
 
 } // namespace blink