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diff --git a/security/sandbox/chromium/base/threading/thread_checker_impl.h b/security/sandbox/chromium/base/threading/thread_checker_impl.h
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+++ b/security/sandbox/chromium/base/threading/thread_checker_impl.h
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+// Copyright (c) 2011 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_IMPL_H_
+#define BASE_THREADING_THREAD_CHECKER_IMPL_H_
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/sequence_token.h"
+#include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
+#include "base/threading/platform_thread.h"
+
+namespace base {
+
+// Real implementation of ThreadChecker, 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 ThreadChecker 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 ThreadCheckerImpl {
+ public:
+  ThreadCheckerImpl();
+  ~ThreadCheckerImpl();
+
+  // Allow move construct/assign. This must be called on |other|'s associated
+  // thread and assignment can only be made into a ThreadCheckerImpl which is
+  // detached or already associated with the current thread. 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 ThreadCheckerImpl
+  // will be bound to the current thread and |other| will be detached.
+  ThreadCheckerImpl(ThreadCheckerImpl&& other);
+  ThreadCheckerImpl& operator=(ThreadCheckerImpl&& other);
+
+  bool CalledOnValidThread() const WARN_UNUSED_RESULT;
+
+  // 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 EnsureAssignedLockRequired() const EXCLUSIVE_LOCKS_REQUIRED(lock_);
+
+  // Members are mutable so that CalledOnValidThread() can set them.
+
+  // Synchronizes access to all members.
+  mutable base::Lock lock_;
+
+  // Thread on which CalledOnValidThread() may return true.
+  mutable PlatformThreadRef thread_id_ GUARDED_BY(lock_);
+
+  // TaskToken for which CalledOnValidThread() always returns true. This allows
+  // CalledOnValidThread() to return true when called multiple times from the
+  // same task, even if it's not running in a single-threaded context itself
+  // (allowing usage of ThreadChecker objects on the stack in the scope of one-
+  // off tasks). Note: CalledOnValidThread() may return true even if the current
+  // TaskToken is not equal to this.
+  mutable TaskToken task_token_ GUARDED_BY(lock_);
+
+  // SequenceToken for which CalledOnValidThread() may return true. Used to
+  // ensure that CalledOnValidThread() doesn't return true for ThreadPool
+  // tasks that happen to run on the same thread but weren't posted to the same
+  // SingleThreadTaskRunner.
+  mutable SequenceToken sequence_token_ GUARDED_BY(lock_);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_CHECKER_IMPL_H_