Enable dartanalyze warnings.

services/dart/test/pingpong/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 'mojo:application';
 import 'mojo:bindings';
 import 'mojo:core';
 
 import 'package:services/dart/test/pingpong_service.mojom.dart';
@@ skipping 33 matching lines @@
     assert(_pingPongClient == null);
     _pingPongClient = proxyBase;
   }
 
   void ping(int pingValue) {
     if (_pingPongClient != null) {
       _pingPongClient.ptr.pong(pingValue + 1);
     }
   }
 
-  Future pingTargetUrl(String url, int count, Function responseFactory) async {
+  Future pingTargetUrl(String url, int count,
+      [Function responseFactory]) async {
     if (_application == null) {
       return responseFactory(false);
     }
     var completer = new Completer();
     var pingPongService = new PingPongServiceProxy.unbound();
     _application.connectToService(url, pingPongService);
 
     var pingPongClient = new PingPongClientImpl.unbound(count, completer);
     pingPongService.ptr.setClient(pingPongClient.stub);
 
     for (var i = 0; i < count; i++) {
       pingPongService.ptr.ping(i);
     }
     await completer.future;
     pingPongService.ptr.quit();
     pingPongService.close();
 
     return responseFactory(true);
   }
 
-  Future pingTargetService(
-      ProxyBase proxyBase, int count, Function responseFactory) async {
+  Future pingTargetService(ProxyBase proxyBase, int count,
+      [Function responseFactory]) async {
     var pingPongService = proxyBase;
     var completer = new Completer();
     var client = new PingPongClientImpl.unbound(count, completer);
     pingPongService.ptr.setClient(client.stub);
 
     for (var i = 0; i < count; i++) {
       pingPongService.ptr.ping(i);
     }
     await completer.future;
     pingPongService.ptr.quit();
@@ skipping 25 matching lines @@
     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);
 }