Roll Observatory packages and add a roll script

packages/observe/benchmark/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.path_benchmark;
+
+import 'package:observe/observe.dart';
+import 'observation_benchmark_base.dart';
+import 'test_path_observable.dart';
+
+class PathBenchmark extends ObservationBenchmarkBase {
+  final PropertyPath path = new PropertyPath('foo.bar.baz');
+
+  PathBenchmark(int objectCount, int mutationCount, String config) : super(
+          'PathBenchmark:$objectCount:$mutationCount:$config', objectCount,
+          mutationCount, config);
+
+  @override
+  int mutateObject(TestPathObservable obj) {
+    switch (config) {
+      case 'leaf':
+        obj.foo.bar.baz += 1;
+        // Make sure [obj.foo.bar] delivers its changes synchronously. The base
+        // class already handles this for [obj].
+        obj.foo.bar.deliverChanges();
+        return 1;
+
+      case 'root':
+        obj.foo = new Foo(obj.foo.bar.baz + 1);
+        return 1;
+
+      default:
+        throw new ArgumentError('Invalid config for PathBenchmark: $config');
+    }
+  }
+
+  @override
+  TestPathObservable newObject() => new TestPathObservable(1);
+
+  @override
+  PathObserver newObserver(TestPathObservable obj) =>
+      new PathObserver(obj, path)..open((_) => mutations--);
+}