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

tools/testing/dart/fletch_warnings_suite.dart

 // 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.
 
 library test.fletch_warnings_suite;
 
 import 'dart:io' as io;
 
 import 'dart:convert' show
     UTF8;
@@ skipping 44 matching lines @@
         commandBuilder.getAnalysisCommand(
             'dart2js-analyze-only',
             dartBinary,
             <String>[
                 '--packages=.packages',  // For the VM.
                 './third_party/dart/pkg/compiler/lib/src/dart2js.dart',
                 '--packages=.packages', // For dart2js.
                 '--library-root=third_party/dart/sdk/',
                 '--analyze-only',
                 '--show-package-warnings',
-                '--categories=Server']..addAll(arguments),
+                '--categories=Server',
+                '--allow-native-extensions']..addAll(arguments),
             null,
             flavor: 'dart2js')];
   }
 }
 
 class FletchWarningsSuite extends TestSuite {
   FletchWarningsSuite(Map configuration, testSuiteDir)
       : super(configuration, "warnings");
 
   void forEachTest(
@@ skipping 51 matching lines @@
 
     var filteredStdout =
         UTF8.decode(stdout, allowMalformed: true).replaceAll(noLintFilter, "");
     if (filteredStdout.isNotEmpty) {
       return Expectation.STATIC_WARNING;
     }
 
     return Expectation.PASS;
   }
 }