Remove unused ConditionVariableWrapper on POSIX platforms

webrtc/system_wrappers/include/condition_variable_wrapper.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_INCLUDE_CONDITION_VARIABLE_WRAPPER_H_
 #define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_CONDITION_VARIABLE_WRAPPER_H_
 
+// TODO(tommi): Remove completely.  As is there is still some code for Windows
+// that relies on ConditionVariableWrapper, but code has been removed on other
+// platforms.
+#if defined(WEBRTC_WIN)
+
 namespace webrtc {
 
 class CriticalSectionWrapper;
 
 class ConditionVariableWrapper {
  public:
   // Factory method, constructor disabled.
   static ConditionVariableWrapper* CreateConditionVariable();
 
   virtual ~ConditionVariableWrapper() {}
 
   // Calling thread will atomically release crit_sect and wait until next
   // some other thread calls Wake() or WakeAll().
   virtual void SleepCS(CriticalSectionWrapper& crit_sect) = 0;
 
   // Same as above but with a timeout.
   virtual bool SleepCS(CriticalSectionWrapper& crit_sect,
                        unsigned long max_time_in_ms) = 0;
 
   // Wakes one thread calling SleepCS().
   virtual void Wake() = 0;
 
   // Wakes all threads calling SleepCS().
   virtual void WakeAll() = 0;
 };
 
 }  // namespace webrtc
 
+#endif  // defined(WEBRTC_WIN)
+
 #endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_CONDITION_VARIABLE_WRAPPER_H_