Get rid of all the library tags.

test/transformer/exclusion/works_on_transformer_group_test.dart

 // Copyright (c) 2014, 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 '../../serve/utils.dart';
 
 const GROUP = """
 import 'package:barback/barback.dart';
 
 import 'transformer.dart';
 
 class RewriteGroup implements TransformerGroup {
@@ skipping 32 matching lines @@
      ]).create();
 
      pubGet();
      pubServe();
      requestShould404("a.out");
      requestShouldSucceed("b.out", "b.txt.out");
      requestShould404("c.out");
      endPubServe();
    });
 }