anchor.diff:  
   import 'dart:async';
   import 'dart:io';
  +import 'dart:math' as math;
   
   import 'package:path/path.dart' as path;
   
  
positive.code: 
  /// Runs a [benchmark] several times and reports the average result.
  Future<double> _run(_Benchmark benchmark) async {
    double total = 0.0;
    for (int i = 0; i < _kRunsPerBenchmark; i++) {
      // Delete cached analysis results.
      rmTree(dir('${Platform.environment['HOME']}/.dartServer'));
  
      total += await benchmark();
    }
    final double average = total / _kRunsPerBenchmark;
    return average;
  }
  
negative.code: import '../framework/utils.dart';
  
  /// Run each benchmark this many times and compute average.
  const int _kRunsPerBenchmark = 4;
  
  /// Runs a benchmark once and reports the result as a lower-is-better numeric
  /// value.
  