Remove barback from the repo.

pkg/barback/test/transformer/aggregate_many_to_one.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.test.transformer.aggregate_many_to_one;
-
-import 'dart:async';
-
-import 'package:barback/barback.dart';
-import 'package:path/path.dart' as path;
-
-import 'mock_aggregate.dart';
-
-/// An [AggregateTransformer] that applies to all assets with a given extension.
-/// For each directory containing any of these assets, it produces an output
-/// file that contains the concatenation of all matched assets in that
-/// directory in alphabetic order by name.
-class AggregateManyToOneTransformer extends MockAggregateTransformer {
-  /// The extension of assets to combine.
-  final String extension;
-
-  /// The basename of the output asset.
-  ///
-  /// The output asset's path will contain the directory name of the inputs as
-  /// well.
-  final String output;
-
-  AggregateManyToOneTransformer(this.extension, this.output);
-
-  String doClassifyPrimary(AssetId id) {
-    if (id.extension != ".$extension") return null;
-    return path.url.dirname(id.path);
-  }
-
-  Future doApply(AggregateTransform transform) {
-    return getPrimaryInputs(transform).toList().then((assets) {
-      assets.sort((asset1, asset2) => asset1.id.path.compareTo(asset2.id.path));
-      return Future.wait(assets.map((asset) => asset.readAsString()));
-    }).then((contents) {
-      var id = new AssetId(transform.package,
-          path.url.join(transform.key, output));
-      transform.addOutput(new Asset.fromString(id, contents.join('\n')));
-    });
-  }
-
-  String toString() => "aggregate $extension->$output";
-}