Fix assert syntax in VM service code.

runtime/bin/vmservice/vmservice_io.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library vmservice_io;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 13 matching lines @@
 
 var _signalWatch;
 var _signalSubscription;
 
 // HTTP servr.
 Server server;
 Future<Server> serverFuture;
 
 _onShutdown() {
   if (server != null) {
-    server.close(true).catchError((e, st) => assert(e));
+    server.close(true).catchError((e, st) { assert(e); });
   }
   if (_signalSubscription != null) {
     _signalSubscription.cancel();
     _signalSubscription = null;
   }
 }
 
 _bootServer() {
   // Load resources.
   _triggerResourceLoad();
@@ skipping 41 matching lines @@
     // It's just here to push an event on the event loop so that we invoke the
     // scheduled microtasks.
     Timer.run(() {});
   }
   scriptLoadPort.handler = _processLoadRequest;
   // Register signal handler after a small delay to avoid stalling main
   // isolate startup.
   new Timer(_shortDelay, _registerSignalHandler);
   return scriptLoadPort;
 }