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

mojo/dart/test/bindings_generation_test.dart

 // Copyright 2014 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 'dart:isolate';
 import 'dart:typed_data';
 import 'dart:convert';
 
 import 'package:_testing/expect.dart';
@@ skipping 285 matching lines @@
 
 void closingProviderIsolate(core.MojoMessagePipeEndpoint endpoint) {
   var provider = new ProviderImpl(endpoint);
   provider._stub.close();
 }
 
 Future<bool> runOnClosedTest() {
   var testCompleter = new Completer();
   var pipe = new core.MojoMessagePipe();
   var proxy = new sample.ProviderProxy.fromEndpoint(pipe.endpoints[0]);
-  proxy.impl.onError = () => testCompleter.complete(true);
+  proxy.impl.onError = (_) => testCompleter.complete(true);
   Isolate.spawn(closingProviderIsolate, pipe.endpoints[1]);
   return testCompleter.future.then((b) {
     Expect.isTrue(b);
   });
 }
 
 main() async {
   testSerializeStructs();
   testUnions();
   await testEnums();
   await testCallResponse();
   await testAwaitCallResponse();
   await runOnClosedTest();
 }