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diff --git a/base/threading/non_thread_safe.h b/base/threading/non_thread_safe.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_NON_THREAD_SAFE_H_
+#define BASE_THREADING_NON_THREAD_SAFE_H_
+#pragma once
+
+#include "base/threading/thread_checker.h"
+
+namespace base {
+
+// A helper class used to help verify that methods of a class are
+// called from the same thread.  One can inherit from this class and use
+// CalledOnValidThread() to verify.
+//
+// This is intended to be used with classes that appear to be thread safe, but
+// aren't.  For example, a service or a singleton like the preferences system.
+//
+// Example:
+// class MyClass : public base::NonThreadSafe {
+//  public:
+//   void Foo() {
+//     DCHECK(CalledOnValidThread());
+//     ... (do stuff) ...
+//   }
+// }
+//
+// In Release mode, CalledOnValidThread will always return true.
+//
+#ifndef NDEBUG
+class NonThreadSafe {
+ public:
+  ~NonThreadSafe();
+
+  bool CalledOnValidThread() const;
+
+ protected:
+  // Changes the thread that is checked for in CalledOnValidThread. The next
+  // call to CalledOnValidThread will attach this class to a new thread. It is
+  // up to the NonThreadSafe derived class to decide to expose this or not.
+  // This may be useful when an object may be created on one thread and then
+  // used exclusively on another thread.
+  void DetachFromThread();
+
+ private:
+  ThreadChecker thread_checker_;
+};
+#else
+// Do nothing in release mode.
+class NonThreadSafe {
+ public:
+  bool CalledOnValidThread() const {
+    return true;
+  }
+
+ protected:
+  void DetachFromThread() {}
+};
+#endif  // NDEBUG
+
+}  // namespace base
+
+#endif  // BASE_NON_THREAD_SAFE_H_