Add debugging prints to the Mac OS directory watcher.

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';
 
 main() {
   initConfig();
+  MacOSDirectoryWatcher.logDebugInfo = true;
 
   watcherFactory = (dir) => new MacOSDirectoryWatcher(dir);
 
   setUp(createSandbox);
 
   sharedTests();
 
   test('DirectoryWatcher creates a MacOSDirectoryWatcher on Mac OS', () {
     expect(new DirectoryWatcher('.'),
         new isInstanceOf<MacOSDirectoryWatcher>());
@@ skipping 35 matching lines @@
       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"));
     });
   });
 }