Remove barback from the repo.

pkg/barback/lib/barback.dart

Index: pkg/barback/lib/barback.dart
diff --git a/pkg/barback/lib/barback.dart b/pkg/barback/lib/barback.dart
deleted file mode 100644
index 3975758597c546d0e7de8bf0b65becb705ea95b4..0000000000000000000000000000000000000000
--- a/pkg/barback/lib/barback.dart
+++ /dev/null
@@ -1,28 +0,0 @@
-// 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;
-
-export 'src/asset/asset.dart';
-export 'src/asset/asset_id.dart';
-export 'src/asset/asset_set.dart';
-export 'src/barback.dart';
-export 'src/build_result.dart';
-export 'src/errors.dart' hide flattenAggregateExceptions;
-export 'src/log.dart';
-export 'src/package_provider.dart';
-export 'src/transformer/aggregate_transform.dart';
-export 'src/transformer/aggregate_transformer.dart';
-export 'src/transformer/barback_settings.dart';
-export 'src/transformer/base_transform.dart';
-export 'src/transformer/declaring_aggregate_transform.dart';
-export 'src/transformer/declaring_aggregate_transformer.dart';
-export 'src/transformer/declaring_transform.dart' hide newDeclaringTransform;
-export 'src/transformer/declaring_transformer.dart';
-export 'src/transformer/lazy_aggregate_transformer.dart';
-export 'src/transformer/lazy_transformer.dart';
-export 'src/transformer/transform.dart' hide newTransform;
-export 'src/transformer/transform_logger.dart';
-export 'src/transformer/transformer.dart';
-export 'src/transformer/transformer_group.dart';