Fix Dartium tests:

tests/lib/math/pi_test.dart

 // Copyright (c) 2012, 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.
 
 // Test that the default PRNG does converge towards Pi when doing a Monte Carlo
 // simulation.
 
 // Library tag to allow Dartium to run the test.
 library pi_test;
 
 import "package:expect/expect.dart";
 import 'dart:math';
 
 var known_bad_seeds = const [
   50051,
   55597,
   59208
 ];
 
-void main(args) {
+void main([args]) {
   // Select a seed either from the argument passed in or
   // otherwise a random seed.
   var seed = -1;
   if ((args != null) && (args.length > 0)) {
     seed = int.parse(args[0]);
   } else {
     var seed_prng = new Random();
     while (seed == -1) {
       seed = seed_prng.nextInt(1<<16);
       if (known_bad_seeds.contains(seed)) {
@@ skipping 16 matching lines @@
       inside++;
     } else {
       outside++;
     }
   }
   // Mmmmh, Pie!
   var pie = 4.0 * (inside/(inside + outside));
   print("$pie");
   Expect.isTrue(((PI - 0.009) < pie) && (pie < (PI + 0.009)));
 }