Roll Observatory packages and add a roll script

watcher/lib/src/directory_watcher.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.directory_watcher;
-
-import 'dart:io';
-
-import 'watch_event.dart';
-import '../watcher.dart';
-import 'directory_watcher/linux.dart';
-import 'directory_watcher/mac_os.dart';
-import 'directory_watcher/windows.dart';
-import 'directory_watcher/polling.dart';
-
-/// Watches the contents of a directory and emits [WatchEvent]s when something
-/// in the directory has changed.
-abstract class DirectoryWatcher implements Watcher {
-  /// The directory whose contents are being monitored.
-  @Deprecated("Expires in 1.0.0. Use DirectoryWatcher.path instead.")
-  String get directory;
-
-  /// Creates a new [DirectoryWatcher] monitoring [directory].
-  ///
-  /// If a native directory watcher is available for this platform, this will
-  /// use it. Otherwise, it will fall back to a [PollingDirectoryWatcher].
-  ///
-  /// If [pollingDelay] is passed, it specifies the amount of time the watcher
-  /// will pause between successive polls of the directory contents. Making this
-  /// shorter will give more immediate feedback at the expense of doing more IO
-  /// and higher CPU usage. Defaults to one second. Ignored for non-polling
-  /// watchers.
-  factory DirectoryWatcher(String directory, {Duration pollingDelay}) {
-    if (FileSystemEntity.isWatchSupported) {
-      if (Platform.isLinux) return new LinuxDirectoryWatcher(directory);
-      if (Platform.isMacOS) return new MacOSDirectoryWatcher(directory);
-      if (Platform.isWindows) return new WindowsDirectoryWatcher(directory);
-    }
-    return new PollingDirectoryWatcher(directory, pollingDelay: pollingDelay);
-  }
-}