Get rid of all the library tags.

test/serve/native_watch_modified_file_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
-
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
 // TODO(nweiz): Default to testing the native watcher and add an explicit test
 // for the polling watcher when issue 14941 is fixed.
 
 main() {
   integration("watches modifications to files when using the native watcher",
       () {
@@ skipping 12 matching lines @@
       d.dir("web", [
         d.file("index.html", "after")
       ])
     ]).create();
 
     waitForBuildSuccess();
     requestShouldSucceed("index.html", "after");
     endPubServe();
   });
 }