Force disconnect all service clients when VM is shutting down

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;
   static const int ID_ERROR_CODE = 4003;
   final WebSocket socket;
 
   WebSocketClient(this.socket, VMService service) : super(service) {
     socket.listen((message) => onWebSocketMessage(message));
     socket.done.then((_) => close());
   }
 
+  disconnect() {
+    if (socket != null) {
+      socket.close();
+    }
+  }
+
   void onWebSocketMessage(message) {
     if (message is String) {
       var map;
       try {
         map = JSON.decode(message);
       } catch (e) {
         socket.close(PARSE_ERROR_CODE, 'Message parse error: $e');
         return;
       }
       if (map is! Map) {
@@ skipping 32 matching lines @@
 
 
 class HttpRequestClient extends Client {
   static ContentType jsonContentType =
       new ContentType("application", "json", charset: "utf-8");
   final HttpRequest request;
 
   HttpRequestClient(this.request, VMService service)
       : super(service, sendEvents:false);
 
+  disconnect() {
+    request.response.close();
+    close();
+  }
+
   void post(String result) {
     if (result == null) {
       close();
       return;
     }
     request.response..headers.contentType = jsonContentType
                     ..write(result)
                     ..close();
     close();
   }
@@ skipping 115 matching lines @@
       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";