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

runtime/vm/atomic_android.h

Index: runtime/vm/atomic_android.h
diff --git a/runtime/vm/atomic_android.h b/runtime/vm/atomic_android.h
index 9f4df90e37b35e5af873339b91e0aa53985ff9e5..8d01ae75a0dfbbe796f205bd21d201cc0f7e50b2 100644
--- a/runtime/vm/atomic_android.h
+++ b/runtime/vm/atomic_android.h
@@ -32,6 +32,13 @@ inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
                                                   uword new_value) {
   return __sync_val_compare_and_swap(ptr, old_value, new_value);
 }
+
+
+inline uint32_t AtomicOperations::CompareAndSwapUint32(uint32_t* ptr,
+                                                       uint32_t old_value,
+                                                       uint32_t new_value) {
+  return __sync_val_compare_and_swap(ptr, old_value, new_value);
+}
 #endif  // !defined(USING_SIMULATOR)
 
 }  // namespace dart