Make NoReloadScope thread safe

runtime/vm/atomic_fuchsia.h

Index: runtime/vm/atomic_fuchsia.h
diff --git a/runtime/vm/atomic_fuchsia.h b/runtime/vm/atomic_fuchsia.h
index 67dd329b66bd169e991fcfafb0a909b61b5ed44b..c44c0803574b55530acdd768d77abe19b4342248 100644
--- a/runtime/vm/atomic_fuchsia.h
+++ b/runtime/vm/atomic_fuchsia.h
@@ -20,6 +20,11 @@ inline uintptr_t AtomicOperations::FetchAndIncrement(uintptr_t* p) {
 }
 
 
+inline intptr_t AtomicOperations::FetchAndIncrement(intptr_t* p) {
+  return __sync_fetch_and_add(p, 1);
+}
+
+
 inline void AtomicOperations::IncrementBy(intptr_t* p, intptr_t value) {
   __sync_fetch_and_add(p, value);
 }
@@ -35,6 +40,11 @@ inline uintptr_t AtomicOperations::FetchAndDecrement(uintptr_t* p) {
 }
 
 
+inline intptr_t AtomicOperations::FetchAndDecrement(intptr_t* p) {
+  return __sync_fetch_and_sub(p, 1);
+}
+
+
 inline void AtomicOperations::DecrementBy(intptr_t* p, intptr_t value) {
   __sync_fetch_and_sub(p, value);
 }