Shutdown the service isolate when shutting down the VM

runtime/bin/vmservice/server.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.
 
 part of vmservice_io;
 
 class WebSocketClient extends Client {
   static const int PARSE_ERROR_CODE = 4000;
   static const int BINARY_MESSAGE_ERROR_CODE = 4001;
   static const int NOT_MAP_ERROR_CODE = 4002;
@@ skipping 162 matching lines @@
       // Server is up and running.
       _notifyServerState(ip, _server.port);
       return this;
     }).catchError((e, st) {
       print('Could not start Observatory HTTP server:\n$e\n$st\n');
       _notifyServerState("", 0);
       return this;
     });
   }
 
+  close(bool force) {
+    if (_server == null) {
+      return new Future.value(null);
+    }
+    return _server.close(force: force);
+  }
+
   Future shutdown(bool forced) {
     if (_server == null) {
       // Not started.
       return new Future.value(this);
     }
 
     // Force displaying of status messages if we are forcibly shutdown.
     _displayMessages = _displayMessages || forced;
 
     // Shutdown HTTP server and subscription.
     var ip = _server.address.address.toString();
     var port = _server.port.toString();
-    return _server.close(force: forced).then((_) {
+    return close(forced).then((_) {
       if (_displayMessages) {
         print('Observatory no longer listening on http://$ip:$port');
       }
       _server = null;
       _notifyServerState("", 0);
       return this;
     }).catchError((e, st) {
       _server = null;
       print('Could not shutdown Observatory HTTP server:\n$e\n$st\n');
       _notifyServerState("", 0);
       return this;
     });
   }
 
 }
 
 void _notifyServerState(String ip, int port)
     native "VMServiceIO_NotifyServerState";