Get rid of all the library tags.

lib/src/digest_sink.dart

 // Copyright (c) 2015, 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 crypto.digest_sink;
-
 import 'digest.dart';
 
 /// A sink used to get a digest value out of [Hash.startChunkedConversion].
 class DigestSink extends Sink<Digest> {
   /// The value added to the sink, if any.
   Digest get value {
     assert(_value != null);
     return _value;
   }
   Digest _value;
 
   /// Adds [value] to the sink.
   ///
   /// Unlike most sinks, this may only be called once.
   void add(Digest value) {
     assert(_value == null);
     _value = value;
   }
 
   void close() {
     assert(_value != null);
   }
 }