Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/observe/observe.dart

Index: observatory_pub_packages/observe/observe.dart
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--- observatory_pub_packages/observe/observe.dart	(revision 0)
+++ observatory_pub_packages/observe/observe.dart	(working copy)
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+// 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.
+
+/// Support for observing changes in model-view architectures.
+///
+/// **Warning:** This library is experimental, and APIs are subject to change.
+///
+/// This library is used to observe changes to [Observable] types. It also
+/// has helpers to make implementing and using [Observable] objects easy.
+///
+/// You can provide an observable object in two ways. The simplest way is to
+/// use dirty checking to discover changes automatically:
+///
+///     import 'package:observe/observe.dart';
+///     import 'package:observe/mirrors_used.dart'; // for smaller code
+///
+///     class Monster extends Unit with Observable {
+///       @observable int health = 100;
+///
+///       void damage(int amount) {
+///         print('$this takes $amount damage!');
+///         health -= amount;
+///       }
+///
+///       toString() => 'Monster with $health hit points';
+///     }
+///
+///     main() {
+///       var obj = new Monster();
+///       obj.changes.listen((records) {
+///         print('Changes to $obj were: $records');
+///       });
+///       // No changes are delivered until we check for them
+///       obj.damage(10);
+///       obj.damage(20);
+///       print('dirty checking!');
+///       Observable.dirtyCheck();
+///       print('done!');
+///     }
+///
+/// A more sophisticated approach is to implement the change notification
+/// manually. This avoids the potentially expensive [Observable.dirtyCheck]
+/// operation, but requires more work in the object:
+///
+///     import 'package:observe/observe.dart';
+///     import 'package:observe/mirrors_used.dart'; // for smaller code
+///
+///     class Monster extends Unit with ChangeNotifier {
+///       int _health = 100;
+///       @reflectable get health => _health;
+///       @reflectable set health(val) {
+///         _health = notifyPropertyChange(#health, _health, val);
+///       }
+///
+///       void damage(int amount) {
+///         print('$this takes $amount damage!');
+///         health -= amount;
+///       }
+///
+///       toString() => 'Monster with $health hit points';
+///     }
+///
+///     main() {
+///       var obj = new Monster();
+///       obj.changes.listen((records) {
+///         print('Changes to $obj were: $records');
+///       });
+///       // Schedules asynchronous delivery of these changes
+///       obj.damage(10);
+///       obj.damage(20);
+///       print('done!');
+///     }
+///
+/// **Note**: by default this package uses mirrors to access getters and setters
+/// marked with `@reflectable`. Dart2js disables tree-shaking if there are any
+/// uses of mirrors, unless you declare how mirrors are used (via the
+/// [MirrorsUsed](https://api.dartlang.org/apidocs/channels/stable/#dart-mirrors.MirrorsUsed)
+/// annotation).
+///
+/// As of version 0.10.0, this package doesn't declare `@MirrorsUsed`. This is
+/// because we intend to use mirrors for development time, but assume that
+/// frameworks and apps that use this pacakge will either generate code that
+/// replaces the use of mirrors, or add the `@MirrorsUsed` declaration
+/// themselves.  For convenience, you can import
+/// `package:observe/mirrors_used.dart` as shown on the first example above.
+/// That will add a `@MirrorsUsed` annotation that preserves properties and
+/// classes labeled with `@reflectable` and properties labeled with
+/// `@observable`.
+///
+/// If you are using the `package:observe/mirrors_used.dart` import, you can
+/// also make use of `@reflectable` on your own classes and dart2js will
+/// preserve all of its members for reflection.
+///
+/// [Tools](https://www.dartlang.org/polymer-dart/) exist to convert the first
+/// form into the second form automatically, to get the best of both worlds.
+library observe;
+
+// This library contains code ported from observe-js:
+// https://github.com/Polymer/observe-js/blob/0152d542350239563d0f2cad39d22d3254bd6c2a/src/observe.js
+// We port what is needed for data bindings. Most of the functionality is
+// ported, except where differences are needed for Dart's Observable type.
+
+export 'src/bindable.dart';
+export 'src/bind_property.dart';
+export 'src/change_notifier.dart';
+export 'src/change_record.dart';
+export 'src/list_path_observer.dart';
+export 'src/list_diff.dart' show ListChangeRecord;
+export 'src/metadata.dart';
+export 'src/observable.dart' hide notifyPropertyChangeHelper;
+export 'src/observable_box.dart';
+export 'src/observable_list.dart';
+export 'src/observable_map.dart';
+export 'src/observer_transform.dart';
+export 'src/path_observer.dart' hide getSegmentsOfPropertyPathForTesting;
+export 'src/to_observable.dart';