Roll Observatory packages and add a roll script

packages/usage/test/all.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 usage.all_test;
+
+import 'hit_types_test.dart' as hit_types_test;
+import 'usage_test.dart' as usage_test;
+import 'usage_impl_test.dart' as usage_impl_test;
+import 'usage_impl_io_test.dart' as usage_impl_io_test;
+import 'uuid_test.dart' as uuid_test;
+
+void main() {
+  hit_types_test.defineTests();
+  usage_test.defineTests();
+  usage_impl_test.defineTests();
+  usage_impl_io_test.defineTests();
+  uuid_test.defineTests();
+}