Update charted to 0.4.8 and roll

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--);
-}