Port async file operations to be using native ports instead or an isolate

runtime/vm/dart_api_message.cc

Index: runtime/vm/dart_api_message.cc
diff --git a/runtime/vm/dart_api_message.cc b/runtime/vm/dart_api_message.cc
index 9f3bcec9b43e7952cfabb9e12af360cfe4dc2d1e..7f8f62919c5ceb265226fa6c035ba6c355b4354b 100644
--- a/runtime/vm/dart_api_message.cc
+++ b/runtime/vm/dart_api_message.cc
@@ -182,14 +182,17 @@ Dart_CObject* ApiMessageReader::ReadInlinedObject(intptr_t object_id) {
     case Object::kTypeArgumentsClass: {
       // TODO(sjesse): Remove this when message serialization format is
       // updated (currently length is leaked).
-      AddBackwardReference(object_id, NULL);
+      Dart_CObject* value = &type_arguments_marker;
+      AddBackwardReference(object_id, value);
       Dart_CObject* length = ReadObject();
       ASSERT(length->type == Dart_CObject::kInt32);
       for (int i = 0; i < length->value.as_int32; i++) {
         Dart_CObject* type = ReadObject();
-        if (type != &dynamic_type_marker) return NULL;
+        if (type != &dynamic_type_marker) {
+          return NULL;
+        }
       }
-      return &type_arguments_marker;
+      return value;
     }
     case ObjectStore::kArrayClass: {
       intptr_t len = ReadSmiValue();