Get rid of all the library tags.

test/trace_test.dart

 // Copyright (c) 2013, the Dart 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 file.
 
-library trace_test;
-
 import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:test/test.dart';
 
 String getStackTraceString() {
   try {
     throw '';
   } catch (_, stackTrace) {
     return stackTrace.toString();
   }
@@ skipping 404 matching lines @@
 ''');
 
       expect(trace.foldFrames((frame) => true).toString(), equals(r'''
 .g"cs$#:b";a#>sw{*{ul$"$xqwr`p
 %+j-?uppx<([j@#nu{{>*+$%x-={`{
 !e($b{nj)zs?cgr%!;bmw.+$j+pfj~
 '''));
     });
   });
 }