anchor.diff:  ///     printer.printToStdout();
   ///
   class BenchmarkResultPrinter {
  -
     final List<_BenchmarkResult> _results = <_BenchmarkResult>[];
   
     /// Adds a benchmark result to the list of results.
  
positive.code:   String _printPlainText() {
      final buf = StringBuffer();
      for (final result in _results) {
        buf.writeln('${result.description}: ${result.value.toStringAsFixed(1)} ${result.unit}');
      }
      return buf.toString();
    }
  
negative.code:   /// result value. [unit] is the unit of measurement, such as "ms", "km", "h".
    /// [name] is a computer-readable name of the result used as a key in the JSON
    /// serialization of the results.
    void addResult(
        {@required String description,
        @required double value,
        @required String unit,
        @required String name}) {
      _results.add(_BenchmarkResult(description, value, unit, name));
    }
  
  