Close socket, and not non-existing outputStream. Fixes crash in HttpServer.

runtime/bin/http_impl.dart

 // Copyright (c) 2012, 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.
 
 class _HttpRequestResponseBase {
   _HttpRequestResponseBase(_HttpConnectionBase this._httpConnection)
       : _contentLength = -1,
         _keepAlive = false,
         _headers = new Map();
 
@@ skipping 614 matching lines @@
     if (_request != null) {
       _request._onDataEnd();
     }
     _request = null;
   }
 
   void _responseDone() {
     // If the connection is closing then close the output stream to
     // fully close the socket.
     if (_closing) {
-      outputStream.close();
+      _socket.close();
     }
     _response = null;
   }
 
   HttpServer _server;
   HttpRequest _request;
   HttpResponse _response;
 
   // Callbacks.
   Function onRequestReceived;
@@ skipping 600 matching lines @@
     sockets.addFirst(socketConn);
     socketConn._markReturned();
   }
 
   Function _onOpen;
   Map<String, Queue<_SocketConnection>> _openSockets;
   Set<_SocketConnection> _activeSockets;
   Timer _evictionTimer;
   bool _shutdown;  // Has this HTTP client been shutdown?
 }