Work around a flake in the Mac OS watcher test on the bots.

pkg/watcher/test/utils.dart

 // Copyright (c) 2012, 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.test.utils;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 
@@ skipping 158 matching lines @@
   } finally {
     _unorderedEventFuture = oldFuture;
   }
 }
 
 /// Expects that the next set of event will be a change of [type] on [path].
 ///
 /// Multiple calls to [expectEvent] require that the events are received in that
 /// order unless they're called in an [inAnyOrder] block.
 void expectEvent(ChangeType type, String path) {
-  var matcher = predicate((e) {
-    return e is WatchEvent && e.type == type &&
-        e.path == p.join(_sandboxDir, p.normalize(path));
-  }, "is $type $path");
-
   if (_unorderedEventFuture != null) {
     // Assign this to a local variable since it will be un-assigned by the time
     // the scheduled callback runs.
     var future = _unorderedEventFuture;
 
     expect(
         schedule(() => future, "should fire $type event on $path"),
-        completion(contains(matcher)));
+        completion(contains(isWatchEvent(type, path))));
   } else {
     var future = currentSchedule.wrapFuture(
         _watcherEvents.elementAt(_nextEvent),
         "waiting for $type event on $path");
 
     expect(
         schedule(() => future, "should fire $type event on $path"),
-        completion(matcher));
+        completion(isWatchEvent(type, path)));
   }
   _nextEvent++;
 }
 
+/// Returns a matcher that matches a [WatchEvent] with the given [type] and
+/// [path].
+Match isWatchEvent(ChangeType type, String path) {
+  return predicate((e) {
+    return e is WatchEvent && e.type == type &&
+        e.path == p.join(_sandboxDir, p.normalize(path));
+  }, "is $type $path");
+}
+
 void expectAddEvent(String path) => expectEvent(ChangeType.ADD, path);
 void expectModifyEvent(String path) => expectEvent(ChangeType.MODIFY, path);
 void expectRemoveEvent(String path) => expectEvent(ChangeType.REMOVE, path);
 
 /// Schedules writing a file in the sandbox at [path] with [contents].
 ///
 /// If [contents] is omitted, creates an empty file. If [updatedModified] is
 /// `false`, the mock file modification time is not changed.
 void writeFile(String path, {String contents, bool updateModified}) {
   if (contents == null) contents = "";
@@ skipping 73 matching lines @@
 void withPermutations(callback(int i, int j, int k), {int limit}) {
   if (limit == null) limit = 3;
   for (var i = 0; i < limit; i++) {
     for (var j = 0; j < limit; j++) {
       for (var k = 0; k < limit; k++) {
         callback(i, j, k);
       }
     }
   }
 }