Update thread annotiation macros to use RTC_ prefix

webrtc/test/direct_transport.h

 /*
  *  Copyright (c) 2013 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_TEST_DIRECT_TRANSPORT_H_
@@ skipping 52 matching lines @@
   int GetAverageDelayMs();
 
  private:
   void SendPackets();
 
   Call* const send_call_;
   Clock* const clock_;
 
   SingleThreadedTaskQueueForTesting* const task_queue_;
   SingleThreadedTaskQueueForTesting::TaskId next_scheduled_task_
-      GUARDED_BY(&sequence_checker_);
+      RTC_GUARDED_BY(&sequence_checker_);
 
   FakeNetworkPipe fake_network_;
 
   rtc::SequencedTaskChecker sequence_checker_;
 };
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_TEST_DIRECT_TRANSPORT_H_