Update thread annotiation macros to use RTC_ prefix

webrtc/video/call_stats.h

Index: webrtc/video/call_stats.h
diff --git a/webrtc/video/call_stats.h b/webrtc/video/call_stats.h
index a9b42804aa8b92b7db313bead92933747ed732d5..efa98adcd9bc548881b5e6ef1a774cd9899e9bd7 100644
--- a/webrtc/video/call_stats.h
+++ b/webrtc/video/call_stats.h
@@ -70,9 +70,9 @@ class CallStats : public Module {
   // The last RTT in the statistics update (zero if there is no valid estimate).
   int64_t max_rtt_ms_;
   int64_t avg_rtt_ms_;
-  int64_t sum_avg_rtt_ms_ GUARDED_BY(crit_);
-  int64_t num_avg_rtt_ GUARDED_BY(crit_);
-  int64_t time_of_first_rtt_ms_ GUARDED_BY(crit_);
+  int64_t sum_avg_rtt_ms_ RTC_GUARDED_BY(crit_);
+  int64_t num_avg_rtt_ RTC_GUARDED_BY(crit_);
+  int64_t time_of_first_rtt_ms_ RTC_GUARDED_BY(crit_);
 
   // All Rtt reports within valid time interval, oldest first.
   std::list<RttTime> reports_;