Dart: Use a RawReceivePort to receive events for Mojo handles.

services/dart/test/pingpong/lib/main.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:mojo/application.dart';
 import 'package:mojo/bindings.dart';
 import 'package:mojo/core.dart';
 
@@ skipping 102 matching lines @@
       ApplicationConnection connection) {
     connection.provideService(PingPongServiceName,
         (endpoint) => new PingPongServiceImpl(this, endpoint));
   }
 }
 
 main(List args) {
   MojoHandle appHandle = new MojoHandle(args[0]);
   String url = args[1];
   new PingPongApplication.fromHandle(appHandle)
-    ..onError = (() {
+    ..onError = ((_) {
       MojoHandle.reportLeakedHandles();
     });
 }