Update remaining core classes to use OVERRIDE / FINAL when needed

Source/core/plugins/DOMPlugin.h

Index: Source/core/plugins/DOMPlugin.h
diff --git a/Source/core/plugins/DOMPlugin.h b/Source/core/plugins/DOMPlugin.h
index 1cc0611a1803258d198648f45204442dd6953494..fe6a40767aa56761de0ae15eb9a82328339b4ecf 100644
--- a/Source/core/plugins/DOMPlugin.h
+++ b/Source/core/plugins/DOMPlugin.h
@@ -32,10 +32,10 @@ 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;