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diff --git a/base/threading/thread_checker.h b/base/threading/thread_checker.h
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+// Copyright (c) 2010 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_
+#pragma once
+
+#ifndef NDEBUG
+#include "base/lock.h"
+#include "base/threading/platform_thread.h"
+#endif // NDEBUG
+
+namespace base {
+
+// Before using this class, please consider using NonThreadSafe as it
+// makes it much easier to determine the nature of your class.
+//
+// A helper class used to help verify that some methods of a class are
+// called from the same thread.  One can inherit from this class and use
+// CalledOnValidThread() to verify.
+//
+// Inheriting from class indicates that one must be careful when using the class
+// with multiple threads. However, it is up to the class document to indicate
+// how it can be used with threads.
+//
+// Example:
+// class MyClass : public ThreadChecker {
+//  public:
+//   void Foo() {
+//     DCHECK(CalledOnValidThread());
+//     ... (do stuff) ...
+//   }
+// }
+//
+// In Release mode, CalledOnValidThread will always return true.
+//
+#ifndef NDEBUG
+class ThreadChecker {
+ public:
+  ThreadChecker();
+  ~ThreadChecker();
+
+  bool CalledOnValidThread() const;
+
+  // Changes the thread that is checked for in CalledOnValidThread.  This may
+  // be useful when an object may be created on one thread and then used
+  // exclusively on another thread.
+  void DetachFromThread();
+
+ private:
+  void EnsureThreadIdAssigned() const;
+
+  mutable Lock lock_;
+  // This is mutable so that CalledOnValidThread can set it.
+  // It's guarded by |lock_|.
+  mutable PlatformThreadId valid_thread_id_;
+};
+#else
+// Do nothing in release mode.
+class ThreadChecker {
+ public:
+  bool CalledOnValidThread() const {
+    return true;
+  }
+
+  void DetachFromThread() {}
+};
+#endif  // NDEBUG
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_CHECKER_H_