Remove unused ConditionVariableWrapper on POSIX platforms

webrtc/system_wrappers/include/condition_variable_wrapper.h

Index: webrtc/system_wrappers/include/condition_variable_wrapper.h
diff --git a/webrtc/system_wrappers/include/condition_variable_wrapper.h b/webrtc/system_wrappers/include/condition_variable_wrapper.h
index 37ca30f0363040c44ba93dfaba03324d2b5e7f65..f88ba707b375ddd304ee6dc14ddadf11c88d437a 100644
--- a/webrtc/system_wrappers/include/condition_variable_wrapper.h
+++ b/webrtc/system_wrappers/include/condition_variable_wrapper.h
@@ -11,6 +11,11 @@
 #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;
@@ -39,4 +44,6 @@ class ConditionVariableWrapper {
 
 }  // namespace webrtc
 
+#endif  // defined(WEBRTC_WIN)
+
 #endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_CONDITION_VARIABLE_WRAPPER_H_