Remove barback from the repo.

pkg/barback/test/transformer/declaring_aggregate_many_to_one.dart

Index: pkg/barback/test/transformer/declaring_aggregate_many_to_one.dart
diff --git a/pkg/barback/test/transformer/declaring_aggregate_many_to_one.dart b/pkg/barback/test/transformer/declaring_aggregate_many_to_one.dart
deleted file mode 100644
index 7f1874130c4609812b516877b88f6a70eda69101..0000000000000000000000000000000000000000
--- a/pkg/barback/test/transformer/declaring_aggregate_many_to_one.dart
+++ /dev/null
@@ -1,23 +0,0 @@
-// 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.test.transformer.declaring_aggregate_many_to_one;
-
-import 'package:barback/barback.dart';
-import 'package:path/path.dart' as path;
-
-import 'aggregate_many_to_one.dart';
-
-/// Like [AggregateManyToOneTransformer], but declares its assets ahead of time.
-class DeclaringAggregateManyToOneTransformer
-    extends AggregateManyToOneTransformer
-    implements DeclaringAggregateTransformer {
-  DeclaringAggregateManyToOneTransformer(String extension, String output)
-      : super(extension, output);
-
-  void declareOutputs(DeclaringAggregateTransform transform) {
-    transform.declareOutput(new AssetId(transform.package,
-        path.url.join(transform.key, output)));
-  }
-}