Relax expectations for events on mac, and allow move events to not have a destination.

tests/standalone/io/file_system_watcher_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 "dart:async";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
@@ skipping 52 matching lines @@
   var file = new File(dir.path + '/file');
   file.createSync();
 
   var watcher = dir.watch();
 
   asyncStart();
   var sub;
   sub = watcher.listen((event) {
     if (event is FileSystemMoveEvent) {
       Expect.isTrue(event.path.endsWith('file'));
-      Expect.isTrue(event.destination.endsWith('file2'));
+      if (event.destination != null) {
+        Expect.isTrue(event.destination.endsWith('file2'));
+      }
       sub.cancel();
       asyncEnd();
       dir.deleteSync(recursive: true);
     }
   }, onError: (e) {
     dir.deleteSync(recursive: true);
     throw e;
   });
 
   runAsync(() => file.renameSync(dir.path + '/file2'));
@@ skipping 76 matching lines @@
         newState = 3;
         break;
 
       case FileSystemEvent.DELETE:
         newState = 4;
         sub.cancel();
         asyncEnd();
         dir.deleteSync();
         break;
     }
-    if (newState < state) throw "Bad state";
+    if (!Platform.isMacOS) {
+      if (newState < state) throw "Bad state";
+    }
     state = newState;
   });
 
   runAsync(() {
     file.createSync();
     file.writeAsStringSync('a');
     file.renameSync(file2.path);
     file2.deleteSync();
   });
 }
@@ skipping 60 matching lines @@
 void main() {
   if (!FileSystemEntity.isWatchSupported) return;
   testWatchCreateFile();
   testWatchModifyFile();
   testWatchMoveFile();
   testWatchDeleteFile();
   testWatchOnlyModifyFile();
   testMultipleEvents();
   testWatchNonRecursive();
 }