Remove unused ConditionVariableWrapper on POSIX platforms

webrtc/system_wrappers/source/condition_variable_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_CONDITION_VARIABLE_POSIX_H_
-#define WEBRTC_SYSTEM_WRAPPERS_SOURCE_CONDITION_VARIABLE_POSIX_H_
-
-#include <pthread.h>
-
-#include "webrtc/system_wrappers/include/condition_variable_wrapper.h"
-#include "webrtc/typedefs.h"
-
-namespace webrtc {
-
-class ConditionVariablePosix : public ConditionVariableWrapper {
- public:
-  static ConditionVariableWrapper* Create();
-  ~ConditionVariablePosix() override;
-
-  void SleepCS(CriticalSectionWrapper& crit_sect) override;
-  bool SleepCS(CriticalSectionWrapper& crit_sect,
-               unsigned long max_time_in_ms) override;
-  void Wake() override;
-  void WakeAll() override;
-
- private:
-  ConditionVariablePosix();
-  int Construct();
-
- private:
-  pthread_cond_t cond_;
-};
-
-}  // namespace webrtc
-
-#endif  // WEBRTC_SYSTEM_WRAPPERS_SOURCE_CONDITION_VARIABLE_POSIX_H_