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diff --git a/security/sandbox/chromium/base/sequence_checker_impl.h b/security/sandbox/chromium/base/sequence_checker_impl.h
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+++ b/security/sandbox/chromium/base/sequence_checker_impl.h
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+// 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_SEQUENCE_CHECKER_IMPL_H_
+#define BASE_SEQUENCE_CHECKER_IMPL_H_
+
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "base/threading/thread_checker_impl.h"
+
+namespace base {
+
+// SequenceCheckerImpl is used to help verify that some methods of a
+// class are called in sequence -- that is, called from the same
+// SequencedTaskRunner. It is a generalization of ThreadChecker; in
+// particular, it behaves exactly like ThreadChecker if constructed
+// on a thread that is not part of a SequencedWorkerPool.
+class BASE_EXPORT SequenceCheckerImpl {
+ public:
+  SequenceCheckerImpl();
+  ~SequenceCheckerImpl();
+
+  // Returns whether the we are being called on the same sequence token
+  // as previous calls. If there is no associated sequence, then returns
+  // whether we are being called on the underlying ThreadChecker's thread.
+  bool CalledOnValidSequencedThread() const;
+
+  // Unbinds the checker from the currently associated sequence. The
+  // checker will be re-bound on the next call to CalledOnValidSequence().
+  void DetachFromSequence();
+
+ private:
+  void EnsureSequenceTokenAssigned() const;
+
+  // Guards all variables below.
+  mutable Lock lock_;
+
+  // Used if |sequence_token_| is not valid.
+  ThreadCheckerImpl thread_checker_;
+  mutable bool sequence_token_assigned_;
+
+  mutable SequencedWorkerPool::SequenceToken sequence_token_;
+
+  DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
+};
+
+}  // namespace base
+
+#endif  // BASE_SEQUENCE_CHECKER_IMPL_H_