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

pkg/watcher/test/no_subscription/shared.dart

Index: pkg/watcher/test/no_subscription/shared.dart
diff --git a/pkg/watcher/test/no_subscription/shared.dart b/pkg/watcher/test/no_subscription/shared.dart
index cd279e1ca2c88086e141b7ec27fb0016bd2b0860..6623ba363f349b76dfc4e86acc23f771828604f0 100644
--- a/pkg/watcher/test/no_subscription/shared.dart
+++ b/pkg/watcher/test/no_subscription/shared.dart
@@ -19,8 +19,7 @@ sharedTests() {
     // Subscribe to the events.
     var completer = new Completer();
     var subscription = watcher.events.listen(wrapAsync((event) {
-      expect(event.type, equals(ChangeType.ADD));
-      expect(event.path, endsWith("file.txt"));
+      expect(event, isWatchEvent(ChangeType.ADD, "file.txt"));
       completer.complete();
     }));
 
@@ -41,10 +40,19 @@ sharedTests() {
     schedule(() {
       completer = new Completer();
       subscription = watcher.events.listen(wrapAsync((event) {
+        // TODO(nweiz): Remove this when either issue 14373 or 14793 is fixed.
+        // Issue 14373 means that the new [Directory.watch] will emit an event
+        // for "unwatched.txt" being created, and issue 14793 means we have to
+        // check the filesystem, which leads us to assume that the file has been
+        // modified.
+        if (Platform.isMacOS && event.path.endsWith("unwatched.txt")) {
+          expect(event, isWatchEvent(ChangeType.MODIFY, "unwatched.txt"));
+          return;
+        }
+
         // We should get an event for the third file, not the one added while
         // we weren't subscribed.
-        expect(event.type, equals(ChangeType.ADD));
-        expect(event.path, endsWith("added.txt"));
+        expect(event, isWatchEvent(ChangeType.ADD, "added.txt"));
         completer.complete();
       }));