ThreadScope concept to check variable accessed on correct thread

webrtc/base/thread_checker.h

 /*
  *  Copyright (c) 2014 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 59 matching lines @@
 //     RTC_DCHECK(thread_checker_.CalledOnValidThread());
 //     ... (do stuff) ...
 //   }
 //
 //  private:
 //   ThreadChecker thread_checker_;
 // }
 //
 // In Release mode, CalledOnValidThread will always return true.
 #if ENABLE_THREAD_CHECKER
-class ThreadChecker : public ThreadCheckerImpl {
+class LOCKABLE ThreadChecker : public ThreadCheckerImpl {
 };
 #else
-class ThreadChecker : public ThreadCheckerDoNothing {
+class LOCKABLE ThreadChecker : public ThreadCheckerDoNothing {
 };
 #endif  // ENABLE_THREAD_CHECKER
 
 #undef ENABLE_THREAD_CHECKER
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_THREAD_CHECKER_H_