Revert "Remaining private libs"

sdk/lib/io/http_session.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";
+part of "io.dart";
 
 const String _DART_SESSION_ID = "DARTSESSID";
 
 // A _HttpSession is a node in a double-linked list, with _next and _prev being
 // the previous and next pointers.
 class _HttpSession implements HttpSession {
   // Destroyed marked. Used by the http connection to see if a session is valid.
   bool _destroyed = false;
   bool _isNew = true;
   DateTime _lastSeen;
@@ skipping 159 matching lines @@
     }
   }
 
   void _stopTimer() {
     if (_timer != null) {
       _timer.cancel();
       _timer = null;
     }
   }
 }