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

runtime/vm/service_test.cc

Index: runtime/vm/service_test.cc
diff --git a/runtime/vm/service_test.cc b/runtime/vm/service_test.cc
index eddb622a868501819dc344788e2bd557b5cebfe6..229ee5dff98a6191aac410a1b0b4b71fc9d3d8bf 100644
--- a/runtime/vm/service_test.cc
+++ b/runtime/vm/service_test.cc
@@ -35,6 +35,7 @@ class ServiceTestMessageHandler : public MessageHandler {
     }
 
     // Parse the message.
+    EXPECT_GT(message->len(), 0);
     Thread* thread = Thread::Current();
     MessageSnapshotReader reader(message->data(), message->len(), thread);
     const Object& response_obj = Object::Handle(reader.ReadObject());