Get rid of all the library tags.

lib/src/barback/asset_environment.dart

 // Copyright (c) 2014, 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 pub.barback.asset_environment;
-
 import 'dart:async';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as path;
 import 'package:watcher/watcher.dart';
 
 import '../cached_package.dart';
 import '../entrypoint.dart';
 import '../exceptions.dart';
@@ skipping 772 matching lines @@
   String toString() => "polling";
 }
 
 class _NoneWatcherType implements WatcherType {
   const _NoneWatcherType();
 
   DirectoryWatcher create(String directory) => null;
 
   String toString() => "none";
 }