Get rid of all the library tags.

lib/src/location_mixin.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 source_span.location_mixin;
-
 import 'location.dart';
 import 'span.dart';
 
 // Note: this class duplicates a lot of functionality of [SourceLocation]. This
 // is because in order for SourceLocation to use SourceLocationMixin,
 // SourceLocationMixin couldn't implement SourceLocation. In SourceSpan we
 // handle this by making the class itself non-extensible, but that would be a
 // breaking change for SourceLocation. So until we want to endure the pain of
 // cutting a release with breaking changes, we duplicate the code here.
 
@@ skipping 25 matching lines @@
   bool operator ==(other) =>
       other is SourceLocation &&
       sourceUrl == other.sourceUrl &&
       offset == other.offset;
 
   int get hashCode => sourceUrl.hashCode + offset;
 
   String toString() => '<$runtimeType: $offset $toolString>';
 }