Go into UPGRADED state in http-parser, when socket is being detached.

sdk/lib/io/http_parser.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;
 
 // Global constants.
 class _Const {
   // Bytes for "HTTP".
   static const HTTP = const [72, 84, 84, 80];
@@ skipping 866 matching lines @@
   }
 
   int get messageType => _messageType;
   int get transferLength => _transferLength;
   bool get upgrade => _connectionUpgrade && _state == _State.UPGRADED;
   bool get persistentConnection => _persistentConnection;
 
   void set responseToMethod(String method) { _responseToMethod = method; }
 
   _HttpDetachedIncoming detachIncoming() {
+    // Simulate detached by marking as upgraded.
+    _state = _State.UPGRADED;
     return new _HttpDetachedIncoming(_socketSubscription,
                                      readUnparsedData());
   }
 
   List<int> readUnparsedData() {
     if (_buffer == null) return null;
     if (_index == _buffer.length) return null;
     var result = _buffer.sublist(_index);
     _releaseBuffer();
     return result;
@@ skipping 139 matching lines @@
     }
   }
 
   void _reportError(error, [stackTrace]) {
     if (_socketSubscription != null) _socketSubscription.cancel();
     _state = _State.FAILURE;
     _controller.addError(error, stackTrace);
     _controller.close();
   }
 }