Update thread annotiation macros to use RTC_ prefix

webrtc/test/frame_generator_capturer.h

Index: webrtc/test/frame_generator_capturer.h
diff --git a/webrtc/test/frame_generator_capturer.h b/webrtc/test/frame_generator_capturer.h
index 44251218afb7eee0e6aecd013801e2ad6b16e904..8f3232c3e4479193e6e7a26711a8e8ffbaf1e2fd 100644
--- a/webrtc/test/frame_generator_capturer.h
+++ b/webrtc/test/frame_generator_capturer.h
@@ -87,14 +87,14 @@ class FrameGeneratorCapturer : public VideoCapturer {
 
   Clock* const clock_;
   bool sending_;
-  rtc::VideoSinkInterface<VideoFrame>* sink_ GUARDED_BY(&lock_);
-  SinkWantsObserver* sink_wants_observer_ GUARDED_BY(&lock_);
+  rtc::VideoSinkInterface<VideoFrame>* sink_ RTC_GUARDED_BY(&lock_);
+  SinkWantsObserver* sink_wants_observer_ RTC_GUARDED_BY(&lock_);
 
   rtc::CriticalSection lock_;
   std::unique_ptr<FrameGenerator> frame_generator_;
 
-  int target_fps_ GUARDED_BY(&lock_);
-  rtc::Optional<int> wanted_fps_ GUARDED_BY(&lock_);
+  int target_fps_ RTC_GUARDED_BY(&lock_);
+  rtc::Optional<int> wanted_fps_ RTC_GUARDED_BY(&lock_);
   VideoRotation fake_rotation_ = kVideoRotation_0;
 
   int64_t first_frame_capture_time_;