Adds a special case for sending an int over a port with the native API.

runtime/vm/json_stream.cc

Index: runtime/vm/json_stream.cc
diff --git a/runtime/vm/json_stream.cc b/runtime/vm/json_stream.cc
index 9f942053c99ed197c36a59a3a9371438e0cae18a..a69eede2b1fb4564fdf6c5dd12bb180524fd059f 100644
--- a/runtime/vm/json_stream.cc
+++ b/runtime/vm/json_stream.cc
@@ -161,16 +161,8 @@ static uint8_t* allocator(uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
 
 
 void JSONStream::PostNullReply(Dart_Port port) {
-  const Object& reply = Object::Handle(Object::null());
-  ASSERT(reply.IsNull());
-
-  uint8_t* data = NULL;
-  MessageWriter writer(&data, &allocator, false);
-  writer.WriteMessage(reply);
-  PortMap::PostMessage(new Message(port,
-                                   data,
-                                   writer.BytesWritten(),
-                                   Message::kNormalPriority));
+  PortMap::PostMessage(new Message(
+      port, Object::null(), Message::kNormalPriority));
 }