Fix the Mac OS directory watcher tests on the bots.

pkg/watcher/test/directory_watcher/mac_os_test.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.
 
 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';
@@ skipping 32 matching lines @@
     writeFile("a.txt", contents: "same");
     writeFile("b.txt", contents: "after");
     expectModifyEvent("a.txt");
     expectModifyEvent("b.txt");
   });
 
   test('emits events for many nested files moved out then immediately back in',
       () {
     withPermutations((i, j, k) =>
         writeFile("dir/sub/sub-$i/sub-$j/file-$k.txt"));
+
+    // We sleep here because a narrow edge case caused by two interacting bugs
+    // can produce events that aren't expected if we start the watcher too
+    // soon after creating the files above. Here's what happens:
+    //
+    // * We create "dir/sub" and its contents above.
+    //
+    // * We initialize the watcher watching "dir".
+    //
+    // * Due to issue 14373, the watcher can receive native events describing
+    //   the creation of "dir/sub" and its contents despite the fact that they
+    //   occurred before the watcher was started.
+    //
+    // * Usually the above events will occur while the watcher is doing its
+    //   initial scan of "dir/sub" and be ignored, but occasionally they will
+    //   occur afterwards.
+    //
+    // * When processing the bogus CREATE events, the watcher has to assume that
+    //   they could mean something other than CREATE (issue 14793). Thus it
+    //   assumes that the files or directories in question could have changed
+    //   and emits CHANGE events or additional REMOVE/CREATE pairs for them.
+    schedule(() => new Future.delayed(new Duration(seconds: 2)));
+
     startWatcher(dir: "dir");
 
     renameDir("dir/sub", "sub");
     renameDir("sub", "dir/sub");
 
     inAnyOrder(() {
       withPermutations((i, j, k) =>
           expectRemoveEvent("dir/sub/sub-$i/sub-$j/file-$k.txt"));
     });
 
     inAnyOrder(() {
       withPermutations((i, j, k) =>
           expectAddEvent("dir/sub/sub-$i/sub-$j/file-$k.txt"));
     });
   });
 }