diff -r 000000000000 -r 6474c204b198 ipc/chromium/src/base/atomic_sequence_num.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/chromium/src/base/atomic_sequence_num.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+// Copyright (c) 2006-2008 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_ATOMIC_SEQUENCE_NUM_H_
+#define BASE_ATOMIC_SEQUENCE_NUM_H_
+
+#include "base/atomicops.h"
+#include "base/basictypes.h"
+
+namespace base {
+
+class AtomicSequenceNumber {
+ public:
+  AtomicSequenceNumber() : seq_(0) { }
+  explicit AtomicSequenceNumber(base::LinkerInitialized x) { /* seq_ is 0 */ }
+
+  int GetNext() {
+    return static_cast<int>(
+        base::subtle::NoBarrier_AtomicIncrement(&seq_, 1) - 1);
+  }
+
+ private:
+  base::subtle::Atomic32 seq_;
+  DISALLOW_COPY_AND_ASSIGN(AtomicSequenceNumber);
+};
+
+}  // namespace base
+
+#endif  // BASE_ATOMIC_SEQUENCE_NUM_H_