Add a Disconnector class.

lib/stream_channel.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 
 import 'package:async/async.dart';
 
 import 'src/guarantee_channel.dart';
 import 'src/stream_channel_transformer.dart';
 
 export 'src/delegating_stream_channel.dart';
+export 'src/disconnector.dart';
 export 'src/isolate_channel.dart';
 export 'src/json_document_transformer.dart';
 export 'src/multi_channel.dart';
 export 'src/stream_channel_completer.dart';
 export 'src/stream_channel_controller.dart';
 export 'src/stream_channel_transformer.dart';
 
 /// An abstract class representing a two-way communication channel.
 ///
 /// Users should consider the [stream] emitting a "done" event to be the
@@ skipping 115 matching lines @@
 
   StreamChannel<T> transformSink(StreamSinkTransformer<T, T> transformer) =>
       changeSink(transformer.bind);
 
   StreamChannel<T> changeStream(Stream<T> change(Stream<T> stream)) =>
       new StreamChannel(change(stream), sink);
 
   StreamChannel<T> changeSink(StreamSink<T> change(StreamSink<T> sink)) =>
       new StreamChannel(stream, change(sink));
 }