Reorganize barback's source files.

pkg/barback/lib/src/utils/stream_replayer.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.
 
-library barback.stream_replayer;
+library barback.utils.stream_replayer;
 
 import 'dart:async';
 import 'dart:collection';
 
-import 'utils.dart';
+import '../utils.dart';
 
 /// Records the values and errors that are sent through a stream and allows them
 /// to be replayed arbitrarily many times.
 ///
 /// This only listens to the wrapped stream when a replayed stream gets a
 /// listener.
 class StreamReplayer<T> {
   /// The wrapped stream.
   final Stream<T> _stream;
 
@@ skipping 53 matching lines @@
       }
     }, onDone: () {
       _isClosed = true;
       for (var controller in _controllers) {
         controller.close();
       }
       _controllers.clear();
     });
   }
 }