Wrap Directory.watch on Mac OS for the watcher package.

pkg/watcher/test/no_subscription/mac_os_test.dart

Index: pkg/watcher/test/no_subscription/mac_os_test.dart
diff --git a/pkg/watcher/test/no_subscription/mac_os_test.dart b/pkg/watcher/test/no_subscription/mac_os_test.dart
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index 0000000000000000000000000000000000000000..3862134d6e4d095045e78be43b7a2dbed03fbf5b
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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.
+
+import 'package:scheduled_test/scheduled_test.dart';
+import 'package:watcher/src/directory_watcher/mac_os.dart';
+import 'package:watcher/watcher.dart';
+
+import 'shared.dart';
+import '../utils.dart';
+
+// This is currently failing due to issue 14793. The reason is fairly complex:
+//
+// 1. As part of the test, an "unwatched.txt" file is created while there are no
+//    active watchers on the containing directory.
+//
+// 2. A watcher is then added.
+//
+// 3. The watcher lists the contents of the directory and notices that
+//    "unwatched.txt" already exists.
+//
+// 4. Since FSEvents reports past changes (issue 14373), the IO event stream
+//    emits a CREATED event for "unwatched.txt".
+//
+// 5. Due to issue 14793, the watcher cannot trust that this is really a CREATED
+//    event and checks the status of "unwatched.txt" on the filesystem against
+//    its internal state.
+//
+// 6. "unwatched.txt" exists on the filesystem and the watcher knows about it
+//    internally as well. It assumes this means that the file was modified.
+//
+// 7. The watcher emits an unexpected MODIFIED event for "unwatched.txt",
+//    causing the test to fail.
+//
+// Once issue 14793 is fixed, this will no longer be the case and the test will
+// work again.
+
+main() {
+  initConfig();
+
+  watcherFactory = (dir) => new MacOSDirectoryWatcher(dir);
+
+  setUp(createSandbox);
+
+  sharedTests();
+}