cleanup and improve A/B fasta test harness

pkg/front_end/tool/fasta/compile.dart

 // Copyright (c) 2017, 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.
 
-import 'package:front_end/src/fasta/outline.dart' as outline;
+import 'package:front_end/src/fasta/outline.dart' show compileEntryPoint;
 
-import 'standard_deviation.dart';
-
-const int iterations = const int.fromEnvironment("iterations", defaultValue: 1);
-
-main(List<String> arguments) async {
-  // Timing results for each iteration
-  List<double> elapseTimes = <double>[];
-
-  for (int i = 0; i < iterations; i++) {
-    if (i > 0) {
-      print("\n");
-    }
-
-    var stopwatch = new Stopwatch()..start();
-    await outline.compile(arguments);
-    stopwatch.stop();
-
-    elapseTimes.add(stopwatch.elapsedMilliseconds.toDouble());
-  }
-
-  // No summary if less than 4 iterations
-  if (elapseTimes.length < 4) {
-    return;
-  }
-
-  // Calculate the mean of warm runs (#4 to n)
-  List<double> warmTimes = elapseTimes.sublist(3);
-  double mean = average(warmTimes);
-
-  // Calculate the standard deviation
-  double stdDev = standardDeviation(mean, warmTimes);
-
-  // Calculate the standard deviation of the mean
-  double stdDevOfTheMean = standardDeviationOfTheMean(warmTimes, stdDev);
-
-  print('Summary:');
-  print('  Elapse times: $elapseTimes');
-  print('  Cold start (first run): ${elapseTimes[0]}');
-  print('  Warm run average (runs #4 to #$iterations): $mean');
-  print('  Warm run standard deviation of the mean: $stdDevOfTheMean');
-}
+main(List<String> arguments) => compileEntryPoint(arguments);