Fix HttpServer after SecureServerSocket no longer is a ServerSocket.

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 2082 matching lines @@
       }
     });
     return result;
   }
 
   _HttpSessionManager _sessionManagerInstance;
 
   // Indicated if the http server has been closed.
   bool closed = false;
 
-  // The server listen socket.
-  final ServerSocket _serverSocket;
+  // The server listen socket. Untyped as it can be both ServerSocket and
+  // SecureServerSocket.
+  final _serverSocket;
   final bool _closeServer;
 
   // Set of currently connected clients.
   final LinkedList<_HttpConnection> _connections
       = new LinkedList<_HttpConnection>();
   StreamController<HttpRequest> _controller;
   // TODO(ajohnsen): Use close queue?
 }
 
 
@@ skipping 397 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)';
 }