Update charted to 0.4.8 and roll

packages/observe/lib/src/metadata.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.src.metadata;
-
-/// Use `@observable` to make a field automatically observable, or to indicate
-/// that a property is observable. This only works on classes that extend or
-/// mix in `Observable`.
-const ObservableProperty observable = const ObservableProperty();
-
-/// An annotation that is used to make a property observable.
-/// Normally this is used via the [observable] constant, for example:
-///
-///     class Monster extends Observable {
-///       @observable int health;
-///     }
-///
-// TODO(sigmund): re-add this to the documentation when it's really true:
-//     If needed, you can subclass this to create another annotation that will
-//     also be treated as observable.
-// Note: observable properties imply reflectable.
-class ObservableProperty {
-  const ObservableProperty();
-}
-
-
-/// This can be used to retain any properties that you wish to access with
-/// Dart's mirror system. If you import `package:observe/mirrors_used.dart`, all
-/// classes or members annotated with `@reflectable` wil be preserved by dart2js
-/// during compilation.  This is necessary to make the member visible to
-/// `PathObserver`, or similar systems, once the code is deployed, if you are
-/// not doing a different kind of code-generation for your app. If you are using
-/// polymer, you most likely don't need to use this annotation anymore.
-const Reflectable reflectable = const Reflectable();
-
-/// An annotation that is used to make a type or member reflectable. This makes
-/// it available to `PathObserver` at runtime. For example:
-///
-///     @reflectable
-///     class Monster extends ChangeNotifier {
-///       int _health;
-///       int get health => _health;
-///       ...
-///     }
-///     ...
-///       // This will work even if the code has been tree-shaken/minified:
-///       final monster = new Monster();
-///       new PathObserver(monster, 'health').changes.listen(...);
-class Reflectable {
-  const Reflectable();
-}