Roll Observatory packages and add a roll script

packages/barback/test/transformer/lazy_aggregate_many_to_one.dart

Index: packages/barback/test/transformer/lazy_aggregate_many_to_one.dart
diff --git a/packages/barback/test/transformer/lazy_aggregate_many_to_one.dart b/packages/barback/test/transformer/lazy_aggregate_many_to_one.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6bd251928179a06d0853e7a825d9e2a80673a2de
--- /dev/null
+++ b/packages/barback/test/transformer/lazy_aggregate_many_to_one.dart
@@ -0,0 +1,18 @@
+// 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.lazy_aggregate_many_to_one;
+
+import 'package:barback/barback.dart';
+
+import 'declaring_aggregate_many_to_one.dart';
+
+/// Like [AggregateManyToOneTransformer], but returns a lazy asset that doesn't
+/// perform the rewrite until it's materialized.
+class LazyAggregateManyToOneTransformer
+    extends DeclaringAggregateManyToOneTransformer
+    implements LazyAggregateTransformer {
+  LazyAggregateManyToOneTransformer(String extension, String output)
+      : super(extension, output);
+}