Clean VM thread shutdown:

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 71 matching lines @@
 const _shortDelay = const Duration(milliseconds: 10);
 
 main() {
   if (_autoStart) {
     _bootServer();
     server.startup();
     // It's just here to push an event on the event loop so that we invoke the
     // scheduled microtasks.
     Timer.run(() {});
   }
+  // TODO(johnmccutchan, turnidge) Creating a VMService object here causes
+  // strange behavior from the legacy debug protocol and coverage tool.
+  // Enable this code, and remove the call to Isolate::KillIsolate() from
+  // service_isolate.cc when the strange behavior is solved.
+  // See: https://github.com/dart-lang/sdk/issues/23977
+  // else {
+  //   var service = new VMService();
+  //   service.onShutdown = _onShutdown;
+  // }
   scriptLoadPort.handler = _processLoadRequest;
   // Register signal handler after a small delay to avoid stalling main
   // isolate startup.
   new Timer(_shortDelay, _registerSignalHandler);
   return scriptLoadPort;
 }