Use platform sized counters for the refcounted classes in base.

base/atomic_ref_count.h

 // 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.
 
 // This is a low level implementation of atomic semantics for reference
 // counting.  Please use base/memory/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;
+typedef subtle::AtomicWord 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
@@ skipping 31 matching lines @@
 // 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) {
   bool res = (subtle::Acquire_Load(ptr) == 0);
   return res;
 }
 
 }  // namespace base
 
 #endif  // BASE_ATOMIC_REF_COUNT_H_