Get rid of all the library tags.

test/serve/allows_arbitrary_modes_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 '../serve/utils.dart';
 
 const TRANSFORMER = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 
 class ModeTransformer extends Transformer {
@@ skipping 28 matching lines @@
         d.file("foo.txt", "foo")
       ])
     ]).create();
 
     pubGet();
     pubServe(args: ["--mode", "depeche"]);
     requestShouldSucceed("foo.out", "depeche");
     endPubServe();
   });
 }