Roll Observatory packages and add a roll script

packages/observe/benchmark/setup_path_benchmark.dart

+// 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 observe.test.benchmark.setup_path_benchmark;
+
+import 'package:observe/observe.dart';
+import 'setup_observation_benchmark_base.dart';
+import 'test_path_observable.dart';
+
+class SetupPathBenchmark extends SetupObservationBenchmarkBase {
+  final PropertyPath path = new PropertyPath('foo.bar.baz');
+
+  SetupPathBenchmark(int objectCount, String config)
+      : super('SetupPathBenchmark:$objectCount:$config', objectCount, config);
+
+  @override
+  TestPathObservable newObject() => new TestPathObservable(1);
+
+  @override
+  PathObserver newObserver(TestPathObservable obj) =>
+      new PathObserver(obj, path)..open(() {});
+}