Untype 'Socket' a few places, where we try to call a hidden function.

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;
 
 const int _OUTGOING_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 2383 matching lines @@
           ..remotePort = socket.remotePort
           ..localPort = socket.port;
     } catch (e) { }
     return null;
   }
 }
 
 
 class _DetachedSocket extends Stream<List<int>> implements Socket {
   final Stream<List<int>> _incoming;
-  final Socket _socket;
+  final _socket;
 
   _DetachedSocket(this._socket, this._incoming);
 
   StreamSubscription<List<int>> listen(void onData(List<int> event),
                                        {Function onError,
                                         void onDone(),
                                         bool cancelOnError}) {
     return _incoming.listen(onData,
                             onError: onError,
                             onDone: onDone,
@@ skipping 287 matching lines @@
   const _RedirectInfo(this.statusCode, this.method, this.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)';
 }