Update thread annotiation macros to use RTC_ prefix

webrtc/test/single_threaded_task_queue.h

Index: webrtc/test/single_threaded_task_queue.h
diff --git a/webrtc/test/single_threaded_task_queue.h b/webrtc/test/single_threaded_task_queue.h
index ecb22b38eb17b619465bf9f743bffabb64df068d..c078bdd07747219925b9e4d5916cd68af19ef19a 100644
--- a/webrtc/test/single_threaded_task_queue.h
+++ b/webrtc/test/single_threaded_task_queue.h
@@ -71,10 +71,10 @@ class SingleThreadedTaskQueueForTesting {
   void RunLoop();
 
   rtc::CriticalSection cs_;
-  std::list<std::unique_ptr<QueuedTask>> tasks_ GUARDED_BY(cs_);
+  std::list<std::unique_ptr<QueuedTask>> tasks_ RTC_GUARDED_BY(cs_);
   rtc::ThreadChecker owner_thread_checker_;
   rtc::PlatformThread thread_;
-  bool running_ GUARDED_BY(cs_);
+  bool running_ RTC_GUARDED_BY(cs_);
 
   TaskId next_task_id_;