Keep track of when a socket has been destroyed

sdk/lib/io/http_impl.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 dart.io;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
   final Completer _dataCompleter = new Completer();
   Stream<List<int>> _stream;
@@ skipping 1908 matching lines @@
           _connections.add(connection);
         },
         onError: _controller.addError,
         onDone: _controller.close);
     return _controller.stream.listen(onData,
                                      onError: onError,
                                      onDone: onDone,
                                      cancelOnError: cancelOnError);
   }
 
-  void close() {
+  Future close() {
     closed = true;
+    Future result;
     if (_serverSocket != null && _closeServer) {
-      _serverSocket.close();
+      result = _serverSocket.close();
+    } else {
+      result = new Future.value();
     }
     if (_sessionManagerInstance != null) {
       _sessionManagerInstance.close();
       _sessionManagerInstance = null;
     }
     for (_HttpConnection connection in _connections.toList()) {
       connection.destroy();
     }
     _connections.clear();
+    return result;
   }
 
   int get port {
     if (closed) throw new HttpException("HttpServer is not bound to a socket");
     return _serverSocket.port;
   }
 
   set sessionTimeout(int timeout) {
     _sessionManager.sessionTimeout = timeout;
   }
@@ skipping 452 matching lines @@
   final Uri location;
 }
 
 String _getHttpVersion() {
   var version = Platform.version;
   // Only include major and minor version numbers.
   int index = version.indexOf('.', version.indexOf('.') + 1);
   version = version.substring(0, index);
   return 'Dart/$version (dart:io)';
 }