Run pub tests against older versions of barback.

third_party/pkg/barback-0.13.0/lib/src/internal_asset.dart

Index: third_party/pkg/barback-0.13.0/lib/src/internal_asset.dart
diff --git a/pkg/barback/lib/src/asset/internal_asset.dart b/third_party/pkg/barback-0.13.0/lib/src/internal_asset.dart
similarity index 96%
copy from pkg/barback/lib/src/asset/internal_asset.dart
copy to third_party/pkg/barback-0.13.0/lib/src/internal_asset.dart
index dfacba5c80e1f90c24ad564288001cf20077f1a2..75b49694e5e689f69f2a1efb461dc62d8cd9f6be 100644
--- a/pkg/barback/lib/src/asset/internal_asset.dart
+++ b/third_party/pkg/barback-0.13.0/lib/src/internal_asset.dart
@@ -2,18 +2,18 @@
 // 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.asset.internal_asset;
+library barback.internal_asset;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
-import '../serialize.dart';
-import '../utils.dart';
-import '../utils/file_pool.dart';
-import '../utils/stream_replayer.dart';
 import 'asset.dart';
 import 'asset_id.dart';
+import 'file_pool.dart';
+import 'serialize.dart';
+import 'stream_replayer.dart';
+import 'utils.dart';
 
 /// Serialize an asset to a form that's safe to send across isolates.
 Map serializeAsset(Asset asset) {