Roll Observatory packages and add a roll script

packages/observe/benchmark/object_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.object_benchmark;
+
+import 'observation_benchmark_base.dart';
+import 'test_observable.dart';
+
+class ObjectBenchmark extends ObservationBenchmarkBase {
+  ObjectBenchmark(int objectCount, int mutationCount, String config) : super(
+          'ObjectBenchmark:$objectCount:$mutationCount:$config', objectCount,
+          mutationCount, config);
+
+  @override
+  int mutateObject(TestObservable obj) {
+    // Modify the first 5 properties.
+    obj.a++;
+    obj.b++;
+    obj.c++;
+    obj.d++;
+    obj.e++;
+    // Return # of modifications.
+    return 5;
+  }
+
+  @override
+  TestObservable newObject() => new TestObservable();
+}