Devirtualize several mediastream class destructors

Source/modules/mediastream/RTCSessionDescription.h

 /*
  * 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:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 28 matching lines @@
 
 namespace WebCore {
 
 class Dictionary;
 class ExceptionState;
 
 class RTCSessionDescription : public RefCounted<RTCSessionDescription>, public ScriptWrappable {
 public:
     static PassRefPtr<RTCSessionDescription> create(const Dictionary&, ExceptionState&);
     static PassRefPtr<RTCSessionDescription> create(WebKit::WebRTCSessionDescription);
-    virtual ~RTCSessionDescription();
 
     String type();
     void setType(const String&, ExceptionState&);
 
     String sdp();
     void setSdp(const String&);
 
     WebKit::WebRTCSessionDescription webSessionDescription();
 
 private:
     explicit RTCSessionDescription(WebKit::WebRTCSessionDescription);
 
     WebKit::WebRTCSessionDescription m_webSessionDescription;
 };
 
 } // namespace WebCore
 
 #endif // RTCSessionDescription_h