Roll Observatory packages and add a roll script

watcher/lib/src/watch_event.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 watcher.watch_event;
-
-/// An event describing a single change to the file system.
-class WatchEvent {
-  /// The manner in which the file at [path] has changed.
-  final ChangeType type;
-
-  /// The path of the file that changed.
-  final String path;
-
-  WatchEvent(this.type, this.path);
-
-  String toString() => "$type $path";
-}
-
-/// Enum for what kind of change has happened to a file.
-class ChangeType {
-  /// A new file has been added.
-  static const ADD = const ChangeType("add");
-
-  /// A file has been removed.
-  static const REMOVE = const ChangeType("remove");
-
-  /// The contents of a file have changed.
-  static const MODIFY = const ChangeType("modify");
-
-  final String _name;
-  const ChangeType(this._name);
-
-  String toString() => _name;
-}