Mark template class RefCountedObject as final.

rtc_base/refcountedobject.h

 /*
  *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #ifndef RTC_BASE_REFCOUNTEDOBJECT_H_
 #define RTC_BASE_REFCOUNTEDOBJECT_H_
 
 #include <utility>
 
 #include "rtc_base/atomicops.h"
 
 namespace rtc {
 
 template <class T>
-class RefCountedObject : public T {
+class RefCountedObject final : public T {
  public:
   RefCountedObject() {}
 
   template <class P0>
   explicit RefCountedObject(P0&& p0) : T(std::forward<P0>(p0)) {}
 
   template <class P0, class P1, class... Args>
   RefCountedObject(P0&& p0, P1&& p1, Args&&... args)
       : T(std::forward<P0>(p0),
           std::forward<P1>(p1),
@@ skipping 21 matching lines @@
 
  protected:
   virtual ~RefCountedObject() {}
 
   mutable volatile int ref_count_ = 0;
 };
 
 }  // namespace rtc
 
 #endif  // RTC_BASE_REFCOUNTEDOBJECT_H_