anchor.diff:      return result;
     }
   }
  -
  -class _Scanner extends Scanner {
  -  _Scanner(String contents) : super.create(new CharSequenceReader(contents)) {
  -    preserveComments = false;
  -  }
  -
  -  @override
  -  void reportError(errorCode, int offset, List<Object> arguments) {
  -    // ignore errors.
  -  }
  -}
  
positive.code:   scanTimer.start();
    // TODO(sigmund): is there a way to scan from a random-access-file without
    // first converting to String?
    var scanner = new _Scanner(source.contents.data);
    var token = scanner.tokenize();
    scanTimer.stop();
    return token;
  }
  
negative.code: import 'package:analyzer/src/summary/idl.dart';
  import 'package:analyzer/src/summary/link.dart';
  import 'package:analyzer/src/summary/summarize_ast.dart';
  import 'package:front_end/src/fasta/scanner.dart';
  import 'package:front_end/src/scanner/token.dart';
  import 'package:package_config/discovery.dart';
  import 'package:path/path.dart' as path;
  