Revert "Switch libraries to using new tags."

sdk/lib/io/socket_stream_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.
 
-part of dart.io;
-
 class _SocketInputStream implements InputStream {
   _SocketInputStream(Socket socket) : _socket = socket {
     if (_socket._closed) _closed = true;
     _socket.onClosed = _onClosed;
   }
 
   List<int> read([int len]) {
     return _socket.read(len);
   }
 
@@ skipping 183 matching lines @@
     }
   }
 
   Socket _socket;
   _BufferList _pendingWrites;
   Function _onNoPendingWrites;
   Function _onClosed;
   bool _closing = false;
   bool _closed = false;
 }