Transition barback's infrastructure to an aggregate-based model.

pkg/barback/lib/src/transformer/declaring_aggregate_transform.dart

 // Copyright (c) 2014, 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.transformer.declaring_aggregate_transform;
 
 import 'dart:async';
 
 import '../asset/asset_id.dart';
 import '../graph/transform_node.dart';
@@ skipping 68 matching lines @@
   }
 }
 
 /// The controller for [DeclaringAggregateTransform].
 class DeclaringAggregateTransformController extends BaseTransformController {
   DeclaringAggregateTransform get transform => super.transform;
 
   /// The set of ids that the transformer declares it will emit.
   Set<AssetId> get outputIds => transform._outputIds;
 
-  /// The controller for the [DeclaringAggregateTransform.primaryIds] stream.
-  StreamController<AssetId> get idController => transform._idController;
+  bool get isDone => transform._idController.isClosed;
 
   DeclaringAggregateTransformController(TransformNode node)
       : super(new DeclaringAggregateTransform._(node));
 
-  void close() {
-    super.close();
-    idController.close();
+  /// Adds a primary input id to the [DeclaringAggregateTransform.primaryIds]
+  /// stream.
+  void addId(AssetId id) => transform._idController.add(id);
+
+  void done() {
+    transform._idController.close();
   }
 }