Implement SequencedTaskChecker.

webrtc/base/sequenced_task_checker_impl.h

Index: webrtc/base/sequenced_task_checker_impl.h
diff --git a/webrtc/base/sequenced_task_checker_impl.h b/webrtc/base/sequenced_task_checker_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..9b76ed60708bd27bdb9b5d52794933eadf264458
--- /dev/null
+++ b/webrtc/base/sequenced_task_checker_impl.h
@@ -0,0 +1,44 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_BASE_SEQUENCED_TASK_CHECKER_IMPL_H_
+#define WEBRTC_BASE_SEQUENCED_TASK_CHECKER_IMPL_H_
+
+#include "webrtc/base/task_queue.h"
+#include "webrtc/base/thread_checker.h"
+
+namespace rtc {
+
+// Real implementation of SequencedTaskChecker, for use in debug mode, or
+// for temporary use in release mode.
+//
+// Note: You should almost always use the SequencedTaskChecker class to get the
+// right version for your build configuration.
+class SequencedTaskCheckerImpl {
+ public:
+  SequencedTaskCheckerImpl();
+  ~SequencedTaskCheckerImpl();
+
+  bool CalledSequentially() const;
+
+  // Changes the task queue or thread that is checked for in IsCurrent.  This
+  // may be useful when an object may be created on one task queue / thread and
+  // then used exclusively on another thread.
+  void Detach();
+
+ private:
+  CriticalSection lock_;
+  ThreadChecker thread_checker_;
+  mutable bool attached_;
+  mutable TaskQueue* valid_queue_;
+};
+
+}  // namespace rtc
+#endif  // WEBRTC_BASE_SEQUENCED_TASK_CHECKER_IMPL_H_