Clean up forward declarations in Source/core

Source/core/plugins/DOMPlugin.h

 /*
     Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
 
     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
@@ skipping 12 matching lines @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/frame/FrameDestructionObserver.h"
 #include "core/plugins/DOMMimeType.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
-class Plugin;
 class PluginData;
 
 class DOMPlugin final : public RefCountedWillBeGarbageCollectedFinalized<DOMPlugin>, public ScriptWrappable, public FrameDestructionObserver {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(DOMPlugin);
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<DOMPlugin> create(PluginData* pluginData, LocalFrame* frame, unsigned index)
     {
         return adoptRefWillBeNoop(new DOMPlugin(pluginData, frame, index));
     }
@@ skipping 15 matching lines @@
     const PluginInfo& pluginInfo() const { return m_pluginData->plugins()[m_index]; }
 
     DOMPlugin(PluginData*, LocalFrame*, unsigned index);
     RefPtr<PluginData> m_pluginData;
     unsigned m_index;
 };
 
 } // namespace blink
 
 #endif // Plugin_h