Add a CompareAndSwapUint32 variant to AtomicOperations so that it is possible to a CAS of a 32 bit …

runtime/vm/atomic_simulator.h

Index: runtime/vm/atomic_simulator.h
diff --git a/runtime/vm/atomic_simulator.h b/runtime/vm/atomic_simulator.h
index 26cde3c668a06d1ffcc5d3db355c58e381bcf276..2b52a227c1f774430a9aaacd6cf4a1922844f589 100644
--- a/runtime/vm/atomic_simulator.h
+++ b/runtime/vm/atomic_simulator.h
@@ -18,6 +18,13 @@ inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
                                                   uword new_value) {
   return Simulator::CompareExchange(ptr, old_value, new_value);
 }
+
+
+inline uint32_t AtomicOperations::CompareAndSwapUint32(uint32_t* ptr,
+                                                       uint32_t old_value,
+                                                       uint32_t new_value) {
+  return Simulator::CompareExchangeUint32(ptr, old_value, new_value);
+}
 #endif  // defined(USING_SIMULATOR)
 
 }  // namespace dart