Mark as closing, when we close the connection manually.

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 475 matching lines @@
     }
   }
 
   bool _writeFrom(List<int> buffer, [int offset, int len]) {
     if (!_error && !_closing) {
       return _socket.outputStream.writeFrom(buffer, offset, len);
     }
   }
 
   bool _close() {
+    _closing = true;
     _socket.close();
   }
 
   void _onData() {
     int available = _socket.available();
     if (available == 0) {
       return;
     }
 
     ByteArray buffer = new ByteArray(available);
     int bytesRead = _socket.readList(buffer, 0, available);
     if (bytesRead > 0) {
       int parsed = _httpParser.writeList(buffer, 0, bytesRead);
       if (parsed != bytesRead) {
         // TODO(sgjesse): Error handling.
-        _socket.close();
+        _close();
       }
     }
   }
 
   void _onClosed() {
     _closing = true;
     _onConnectionClosed(null);
   }
 
   void _onError(Exception e) {
@@ skipping 49 matching lines @@
       if (_request != null && _request._streamErrorHandler != null) {
         _request._streamErrorHandler(e);
       }
       if (_response != null && _response._streamErrorHandler != null) {
         _response._streamErrorHandler(e);
       }
     }
 
     // If currently not processing any request just close the socket.
     if (_httpParser.isIdle) {
-      _socket.close();
+      _close();
       if (onClosed != null && e == null) {
         // Don't call onClosed if onError has been called.
         onClosed();
       }
       return;
     }
 
     // Processing a request.
     if (e == null) {
       // Indicate connection close to the HTTP parser.
@@ skipping 83 matching lines @@
     _server = serverSocket;
     _closeServer = false;
   }
 
   void close() {
     if (_server !== null && _closeServer) {
       _server.close();
     }
     _server = null;
     for (_HttpConnection connection in _connections) {
-      connection._socket.close();
+      connection._close();
     }
     _connections.clear();
   }
 
   int get port() {
     if (_server === null) {
       throw new HttpException("The HttpServer is not listening on a port.");
     }
     return _server.port;
   }
@@ skipping 549 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?
 }