Roll Observatory packages and add a roll script

packages/observe/benchmark/setup_observable_list_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_observable_list_benchmark;
+
+import 'package:observe/observe.dart';
+import 'setup_observation_benchmark_base.dart';
+
+class SetupObservableListBenchmark extends SetupObservationBenchmarkBase {
+  final int elementCount = 100;
+
+  SetupObservableListBenchmark(int objectCount, String config) : super(
+          'SetupObservableListBenchmark:$objectCount:$config', objectCount,
+          config);
+
+  @override
+  ObservableList newObject() {
+    var list = new ObservableList();
+    for (int i = 0; i < elementCount; i++) {
+      list.add(i);
+    }
+    list.deliverChanges();
+    list.deliverListChanges();
+    return list;
+  }
+}