WARN_UNUSED_RESULT on all Thread/SequenceChecker impls

base/threading/thread_checker.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_THREADING_THREAD_CHECKER_H_
 #define BASE_THREADING_THREAD_CHECKER_H_
 
+#include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/threading/thread_checker_impl.h"
 
 // ThreadChecker is a helper class used to help verify that some methods of a
 // class are called from the same thread (for thread-affinity).
 //
 // Use the macros below instead of the ThreadChecker directly so that the unused
 // member doesn't result in an extra byte (four when padded) per instance in
 // production.
 //
@@ skipping 74 matching lines @@
 class ThreadChecker : public ThreadCheckerImpl {
 };
 #else
 class ThreadChecker : public ThreadCheckerDoNothing {
 };
 #endif  // DCHECK_IS_ON()
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_CHECKER_H_