Fix all strong-mode warnings.

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 67 matching lines @@
       throw new StateError(
           "$id can't be consumed because it's not a primary input.");
     }
 
     super.consumePrimary(id);
   }
 }
 
 /// The controller for [DeclaringAggregateTransform].
 class DeclaringAggregateTransformController extends BaseTransformController {
-  DeclaringAggregateTransform get transform => super.transform;
+  final DeclaringAggregateTransform transform;
 
   /// The set of ids that the transformer declares it will emit.
   Set<AssetId> get outputIds => transform._outputIds;
 
   bool get isDone => transform._idController.isClosed;
 
   DeclaringAggregateTransformController(TransformNode node)
-      : super(new DeclaringAggregateTransform._(node));
+      : transform = new DeclaringAggregateTransform._(node);
 
   /// Adds a primary input id to the [DeclaringAggregateTransform.primaryIds]
   /// stream.
   void addId(AssetId id) => transform._idController.add(id);
 
   void done() {
     transform._idController.close();
   }
 }