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

DEPS

 # 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.
 
 
 vars = {
   # NOTE: This revision will be used for looking at
   #   gs://chromium-browser-clang/Mac/clang-<rev>-1.tgz
   #   gs://chromium-browser-clang/Linux_x64/clang-<rev>-1.tgz
   "clang_rev": "245965",
@@ skipping 117 matching lines @@
       '--no_resume',
       '--bucket',
       'dart-dependencies-fletch',
       '-d',
       '-r',
       '--auto_platform',
       'fletch/tools/testing/bin',
     ],
   },
   {
+    'name': 'mdns_native_extension_binaries',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--bucket',
+      'dart-dependencies-fletch',
+      '-d',
+      'fletch/pkg/mdns/lib/native',
+    ],
+  },
+  {
     'name': 'third_party_qemu',
     'pattern': '.',
     'action': [
       'download_from_google_storage',
       '--no_auth',
       '--no_resume',
       '--bucket',
       'dart-dependencies-fletch',
       '-d',
       '-r',
@@ skipping 28 matching lines @@
     ],
   },
   {
     'name': 'GYP',
     'pattern': '.',
     'action': [
       'ninja', '-C', 'fletch',
     ],
   },
 ]