Improve support for multiselect list box accessibility on Windows.

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.
 //
 // The implementation includes annotations to avoid some false positives
 // when using data race detection tools.
 
@@ skipping 33 matching lines @@
   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);
 }
 
+// Increment a reference count by 1 and return the new value.
+inline AtomicRefCount AtomicRefCountIncAndReturnValue(
+    volatile AtomicRefCount *ptr) {
+  ANNOTATE_HAPPENS_BEFORE(ptr);
+  AtomicRefCount res = subtle::Barrier_AtomicIncrement(ptr, 1);
+  ANNOTATE_HAPPENS_AFTER(ptr);
+  return res;
+}
+
+// Decrement a reference count by 1 and return the new value.
+inline AtomicRefCount AtomicRefCountDecAndReturnValue(
+    volatile AtomicRefCount *ptr) {
+  ANNOTATE_HAPPENS_BEFORE(ptr);
+  AtomicRefCount res = subtle::Barrier_AtomicIncrement(ptr, -1);
+  ANNOTATE_HAPPENS_AFTER(ptr);
+  return res;
+}
+
 // 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) {
   bool res = (subtle::Acquire_Load(ptr) == 1);
   if (res) {
     ANNOTATE_HAPPENS_AFTER(ptr);
   }
   return res;
 }
 
 // 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) {
   bool res = (subtle::Acquire_Load(ptr) == 0);
   if (res) {
     ANNOTATE_HAPPENS_AFTER(ptr);
   }
   return res;
 }
 
 }  // namespace base
 
 #endif  // BASE_ATOMIC_REF_COUNT_H_