Revert "Extend the mDNS package with a native extension used on Mac OS"

pkg/mdns/test/native_extension_test.dart

Index: pkg/mdns/test/native_extension_test.dart
diff --git a/pkg/mdns/test/native_extension_test.dart b/pkg/mdns/test/native_extension_test.dart
deleted file mode 100644
index e3d4b641f6efb84771d8db554cdb91494a1aa60c..0000000000000000000000000000000000000000
--- a/pkg/mdns/test/native_extension_test.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2015, the Fletch 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.md file.
-
-import 'dart:async';
-
-import 'package:expect/expect.dart';
-import 'package:mdns/src/native_extension_client.dart';
-
-Future<Null> main() async {
-  String message1 = 'Hello, world!';
-  String result1 = await nativeExtensionEchoTest(message1);
-  Expect.equals(message1, result1);
-
-  List<int> message2 = [1, 2];
-  List<int> result2 = await nativeExtensionEchoTest(message2);
-  Expect.listEquals(message2, result2);
-}