Get rid of all the library tags.

test/transformer/exclusion/works_on_aggregate_transformer_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 AGGREGATE_TRANSFORMER = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as p;
 
@@ skipping 45 matching lines @@
         d.file("d.txt", "d")
       ])
     ]).create();
 
     pubGet();
     pubServe();
     requestShouldSucceed("out.txt", "b\nc");
     endPubServe();
   });
 }