Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/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);
+  }
+}