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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
@@ -0,0 +1,63 @@
+// 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 <memory>
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
+
+namespace base {
+
+// Real implementation of SequenceChecker for use in debug mode or for temporary
+// use in release mode (e.g. to CHECK on a threading issue seen only in the
+// wild).
+//
+// Note: You should almost always use the SequenceChecker class to get the right
+// version for your build configuration.
+// Note: This is only a check, not a "lock". It is marked "LOCKABLE" only in
+// order to support thread_annotations.h.
+class LOCKABLE BASE_EXPORT SequenceCheckerImpl {
+ public:
+  SequenceCheckerImpl();
+  ~SequenceCheckerImpl();
+
+  // Allow move construct/assign. This must be called on |other|'s associated
+  // sequence and assignment can only be made into a SequenceCheckerImpl which
+  // is detached or already associated with the current sequence. This isn't
+  // thread-safe (|this| and |other| shouldn't be in use while this move is
+  // performed). If the assignment was legal, the resulting SequenceCheckerImpl
+  // will be bound to the current sequence and |other| will be detached.
+  SequenceCheckerImpl(SequenceCheckerImpl&& other);
+  SequenceCheckerImpl& operator=(SequenceCheckerImpl&& other);
+
+  // Returns true if called in sequence with previous calls to this method and
+  // the constructor.
+  bool CalledOnValidSequence() const WARN_UNUSED_RESULT;
+
+  // Unbinds the checker from the currently associated sequence. The checker
+  // will be re-bound on the next call to CalledOnValidSequence().
+  void DetachFromSequence();
+
+ private:
+  class Core;
+
+  // Calls straight to ThreadLocalStorage::HasBeenDestroyed(). Exposed purely
+  // for 'friend' to work.
+  static bool HasThreadLocalStorageBeenDestroyed();
+
+  mutable Lock lock_;
+  mutable std::unique_ptr<Core> core_ GUARDED_BY(lock_);
+
+  DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
+};
+
+}  // namespace base
+
+#endif  // BASE_SEQUENCE_CHECKER_IMPL_H_