Revert "Remove Expect from core library."

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';
 
 void main() {
   var seed = new Random().nextInt(1<<16);
   print("pi_test seed: $seed");
   var prng = new Random(seed);
   var outside = 0;
   var inside = 0;
   for (var i = 0; i < 600000; i++) {
     var x = prng.nextDouble();
     var y = prng.nextDouble();
     if ((x*x) + (y*y) < 1.0) {
       inside++;
     } else {
       outside++;
     }
   }
   // Mmmmh, Pie!
   var pie = 4.0 * (inside/(inside + outside));
   print("$pie");
   Expect.isTrue(((PI - 0.009) < pie) && (pie < (PI + 0.009)));
 }