Revert "Switch libraries to using new tags."

sdk/lib/io/stream_util.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;
-
 abstract class _BaseDataInputStream {
   int available();
 
   List<int> read([int len]) {
     if (_closeCallbackCalled || _scheduledCloseCallback != null) return null;
     int bytesToRead = available();
     if (bytesToRead == 0) {
       _checkScheduleCallbacks();
       return null;
     }
@@ skipping 185 matching lines @@
   void _reportError(e) {
     if (_onError != null) {
       _onError(e);
     } else {
       throw e;
     }
   }
 
   Function _onError;
 }