Dart: Fixes bug in MojoEventStreamListener

services/dart/dart_apptests/echo_apptests.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 'mojo:application';
 import 'mojo:bindings';
 import 'mojo:core';
 
 import 'package:apptest/apptest.dart';
 import 'package:services/dart/test/echo_service.mojom.dart';
 
 echoApptests(Application application) {
   group('Echo Service Apptests', () {
-    test('String', () { (() async {
+    test('String', () async {
       var echoProxy = new EchoServiceProxy.unbound();
       application.connectToService("mojo:dart_echo", echoProxy);
 
       var v = await echoProxy.ptr.echoString("foo");
       expect(v.value, equals("foo"));
 
       var q = await echoProxy.ptr.echoString("quit");
       expect(q.value, equals("quit"));
-    })().then(expectAsync((_) => null));});
 
-    test('Empty String', () { (() async {
+      echoProxy.close();
+    });
+
+    test('Empty String', () async {
       var echoProxy = new EchoServiceProxy.unbound();
       application.connectToService("mojo:dart_echo", echoProxy);
 
       var v = await echoProxy.ptr.echoString("");
       expect(v.value, equals(""));
 
       var q = await echoProxy.ptr.echoString("quit");
       expect(q.value, equals("quit"));
-    })().then(expectAsync((_) => null));});
 
-    test('Null String', () { (() async {
+      echoProxy.close();
+    });
+
+    test('Null String', () async {
       var echoProxy = new EchoServiceProxy.unbound();
       application.connectToService("mojo:dart_echo", echoProxy);
 
       var v = await echoProxy.ptr.echoString(null);
       expect(v.value, equals(null));
 
       var q = await echoProxy.ptr.echoString("quit");
       expect(q.value, equals("quit"));
-    })().then(expectAsync((_) => null));});
+
+      echoProxy.close();
+    });
   });
 }