Make StreamSubscription be the active part of a stream.

sdk/lib/io/mime_multipart_parser.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;
 
 
 /**
  * A Mime Multipart class representing each part parsed by
  * [MimeMultipartTransformer]. The data is streamed in as it become available.
@@ skipping 83 matching lines @@
   void _resumeStream() {
     _subscription.resume();
   }
 
   void _pauseStream() {
     _subscription.pause();
   }
 
   Stream<MimeMultipart> bind(Stream<List<int>> stream) {
     _controller = new StreamController(
-        onPause: () {
-          _pauseStream();
-        },
-        onResume: () {
-          _resumeStream();
+        onPause: _pauseStream,
+        onResume:_resumeStream,
+        onCancel: () {
+          _subscription.cancel();
         },
         onListen: () {
           _subscription = stream.listen(
               (data) {
                 assert(_buffer == null);
                 _pauseStream();
                 _buffer = data;
                 _index = 0;
                 _parse();
               },
               onDone: () {
                 if (_state != _DONE) {
                   _controller.addError(
                       new MimeMultipartException("Bad multipart ending"));
                 }
                 _controller.close();
               },
               onError: (error) {
                 _controller.addError(error);
               });
-        },
-        onCancel: () {
-          _subscription.cancel();
         });
     return _controller.stream;
   }
 
   void _parse() {
     // Number of boundary bytes to artificially place before the supplied data.
     int boundaryPrefix = 0;
     // Position where content starts. Will be null if no known content
     // start exists. Will be negative of the content starts in the
     // boundary prefix. Will be zero or position if the content starts
@@ skipping 256 matching lines @@
     }
   }
 }
 
 
 class MimeMultipartException implements Exception {
   const MimeMultipartException([String this.message = ""]);
   String toString() => "MimeMultipartException: $message";
   final String message;
 }