diff -r 000000000000 -r 6474c204b198 ipc/chromium/src/base/atomic_ref_count.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/chromium/src/base/atomic_ref_count.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+// 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.
+
+// This is a low level implementation of atomic semantics for reference
+// counting.  Please use base/ref_counted.h directly instead.
+
+#ifndef BASE_ATOMIC_REF_COUNT_H_
+#define BASE_ATOMIC_REF_COUNT_H_
+
+#include "base/atomicops.h"
+
+namespace base {
+
+typedef subtle::Atomic32 AtomicRefCount;
+
+// Increment a reference count by "increment", which must exceed 0.
+inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,
+                               AtomicRefCount increment) {
+  subtle::NoBarrier_AtomicIncrement(ptr, increment);
+}
+
+// Decrement a reference count by "decrement", which must exceed 0,
+// and return whether the result is non-zero.
+// Insert barriers to ensure that state written before the reference count
+// became zero will be visible to a thread that has just made the count zero.
+inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,
+                               AtomicRefCount decrement) {
+  return subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0;
+}
+
+// Increment a reference count by 1.
+inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {
+  base::AtomicRefCountIncN(ptr, 1);
+}
+
+// Decrement a reference count by 1 and return whether the result is non-zero.
+// Insert barriers to ensure that state written before the reference count
+// became zero will be visible to a thread that has just made the count zero.
+inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {
+  return base::AtomicRefCountDecN(ptr, 1);
+}
+
+// Return whether the reference count is one.  If the reference count is used
+// in the conventional way, a refrerence count of 1 implies that the current
+// thread owns the reference and no other thread shares it.  This call performs
+// the test for a reference count of one, and performs the memory barrier
+// needed for the owning thread to act on the object, knowing that it has
+// exclusive access to the object.
+inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {
+  return subtle::Acquire_Load(ptr) == 1;
+}
+
+// Return whether the reference count is zero.  With conventional object
+// referencing counting, the object will be destroyed, so the reference count
+// should never be zero.  Hence this is generally used for a debug check.
+inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {
+  return subtle::Acquire_Load(ptr) == 0;
+}
+
+}  // namespace base
+
+#endif  // BASE_ATOMIC_REF_COUNT_H_