Roll Observatory packages and add a roll script

packages/unittest/test/runtests_without_tests_test.dart

Index: packages/unittest/test/runtests_without_tests_test.dart
diff --git a/packages/unittest/test/runtests_without_tests_test.dart b/packages/unittest/test/runtests_without_tests_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4257ddaa381e305f0480e3a47144b80623ae23c8
--- /dev/null
+++ b/packages/unittest/test/runtests_without_tests_test.dart
@@ -0,0 +1,19 @@
+// 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 unittest.runtests_without_tests;
+
+import 'package:unittest/unittest.dart';
+
+import 'package:metatest/metatest.dart';
+
+void main() => initTests(_test);
+
+void _test(message) {
+  initMetatest(message);
+
+  expectTestResults('runTests() without tests', () {
+    group('no tests', () {});
+  }, []);
+}