Update remaining core classes to use OVERRIDE / FINAL when needed

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 14 matching lines @@
 #include "core/plugins/DOMMimeType.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 class Plugin;
 class PluginData;
 
-class DOMPlugin : public ScriptWrappable, public RefCounted<DOMPlugin>, public FrameDestructionObserver {
+class DOMPlugin FINAL : public ScriptWrappable, public RefCounted<DOMPlugin>, public FrameDestructionObserver {
 public:
     static PassRefPtr<DOMPlugin> create(PluginData* pluginData, Frame* frame, unsigned index) { return adoptRef(new DOMPlugin(pluginData, frame, index)); }
-    ~DOMPlugin();
+    virtual ~DOMPlugin();
 
     String name() const;
     String filename() const;
     String description() const;
 
     unsigned length() const;
 
     PassRefPtr<DOMMimeType> item(unsigned index);
     bool canGetItemsForName(const AtomicString& propertyName);
     PassRefPtr<DOMMimeType> namedItem(const AtomicString& propertyName);
 
 private:
     const PluginInfo& pluginInfo() const { return m_pluginData->plugins()[m_index]; }
 
     DOMPlugin(PluginData*, Frame*, unsigned index);
     RefPtr<PluginData> m_pluginData;
     unsigned m_index;
 };
 
 } // namespace WebCore
 
 #endif // Plugin_h