Update thread annotiation macros in rtc_base to use RTC_ prefix

webrtc/rtc_base/sequenced_task_checker_unittest.cc

 /*
  *  Copyright (c) 2016 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.
  */
 
@@ skipping 219 matching lines @@
 class TestAnnotations {
  public:
   TestAnnotations() : test_var_(false) {}
 
   void ModifyTestVar() {
     RTC_DCHECK_CALLED_SEQUENTIALLY(&checker_);
     test_var_ = true;
   }
 
  private:
-  bool test_var_ GUARDED_BY(&checker_);
+  bool test_var_ RTC_GUARDED_BY(&checker_);
   SequencedTaskChecker checker_;
 };
 
 TEST(SequencedTaskCheckerTest, TestAnnotations) {
   TestAnnotations annotations;
   annotations.ModifyTestVar();
 }
 
 #if GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
 
@@ skipping 13 matching lines @@
 TEST(SequencedTaskCheckerTest, TestAnnotationsOnWrongQueueDebug) {
   ASSERT_DEATH({ TestAnnotationsOnWrongQueue(); }, "");
 }
 #else
 TEST(SequencedTaskCheckerTest, TestAnnotationsOnWrongQueueRelease) {
   TestAnnotationsOnWrongQueue();
 }
 #endif
 #endif  // GTEST_HAS_DEATH_TEST
 }  // namespace rtc