Make CriticalSectionWrapper non-virtual

webrtc/system_wrappers/source/critical_section_posix.h

-/*
- *  Copyright (c) 2011 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 WEBRTC_SYSTEM_WRAPPERS_SOURCE_CRITICAL_SECTION_POSIX_H_
-#define WEBRTC_SYSTEM_WRAPPERS_SOURCE_CRITICAL_SECTION_POSIX_H_
-
-#include "webrtc/system_wrappers/include/critical_section_wrapper.h"
-
-#include <pthread.h>
-
-namespace webrtc {
-
-class CriticalSectionPosix : public CriticalSectionWrapper {
- public:
-  CriticalSectionPosix();
-
-  ~CriticalSectionPosix() override;
-
-  void Enter() override;
-  void Leave() override;
-
- private:
-  pthread_mutex_t mutex_;
-  friend class ConditionVariablePosix;
-};
-
-}  // namespace webrtc
-
-#endif  // WEBRTC_SYSTEM_WRAPPERS_SOURCE_CRITICAL_SECTION_POSIX_H_