Get rid of all the library tags.

lib/src/span_mixin.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 source_span.span_mixin;
-
 import 'dart:math' as math;
 import 'package:path/path.dart' as p;
 
 import 'colors.dart' as colors;
 import 'span.dart';
 import 'span_with_context.dart';
 import 'utils.dart';
 
 /// A mixin for easily implementing [SourceSpan].
 ///
@@ skipping 80 matching lines @@
     return buffer.toString();
   }
 
   bool operator ==(other) => other is SourceSpan &&
       start == other.start && end == other.end;
 
   int get hashCode => start.hashCode + (31 * end.hashCode);
 
   String toString() => '<$runtimeType: from $start to $end "$text">';
 }