Update more platform classes to use OVERRIDE / FINAL when needed

Source/platform/drm/ContentDecryptionModuleSession.h

 /*
  * Copyright (C) 2013 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 42 matching lines @@
     virtual void keyError(MediaKeyErrorCode, unsigned long systemCode) = 0;
     virtual void keyMessage(const unsigned char* message, size_t messageLength, const KURL& destinationURL) = 0;
 };
 
 class PLATFORM_EXPORT ContentDecryptionModuleSession : private blink::WebContentDecryptionModuleSession::Client {
     WTF_MAKE_NONCOPYABLE(ContentDecryptionModuleSession);
 public:
     static PassOwnPtr<ContentDecryptionModuleSession> create(ContentDecryptionModuleSessionClient*);
 
     ContentDecryptionModuleSession(blink::WebContentDecryptionModule*, ContentDecryptionModuleSessionClient*);
-    ~ContentDecryptionModuleSession();
+    virtual ~ContentDecryptionModuleSession();
 
     String sessionId() const;
     void initializeNewSession(const String& mimeType, const Uint8Array& initData);
     void update(const Uint8Array& response);
     void release();
 
 private:
     // blink::WebContentDecryptionModuleSession::Client
     virtual void keyAdded() OVERRIDE;
     virtual void keyError(MediaKeyErrorCode, unsigned long systemCode) OVERRIDE;
     virtual void keyMessage(const unsigned char* message, size_t messageLength, const blink::WebURL& destinationURL) OVERRIDE;
 
     OwnPtr<blink::WebContentDecryptionModuleSession> m_session;
 
     ContentDecryptionModuleSessionClient* m_client;
 };
 
 } // namespace WebCore
 
 #endif // ContentDecryptionModuleSession_h