Make corelib_strong tests strong-mode compliant

tests/corelib_strong/shuffle_test.dart

 // Copyright (c) 2011, 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.
 
 // Dart test for List.shuffle.
 library shuffle_test;
 import "dart:typed_data";
 import "dart:math" show Random;
 import "package:expect/expect.dart";
 
@@ skipping 77 matching lines @@
     }
   }
   if (!listsDifferent()) {
     Expect.fail("Didn't shuffle at all, p < 1:1e80: $list");
   }
 }
 
 
 // Checks that the "random" argument to shuffle is used.
 testRandom() {
-  List randomNums = [37, 87, 42, 157, 252, 17];
+  List<int> randomNums = [37, 87, 42, 157, 252, 17];
   List numbers = new List.generate(25, (x) => x);
   List l1 = numbers.toList()..shuffle(new MockRandom(randomNums));
   for (int i = 0; i < 50; i++) {
     // With same random sequence, we get the same shuffling each time.
     List l2 = numbers.toList()..shuffle(new MockRandom(randomNums));
     Expect.listEquals(l1, l2);
   }
 }
 
 class MockRandom implements Random {
   final List<int> _values;
   int index = 0;
   MockRandom(this._values);
 
   int get _next {
     int next = _values[index];
     index = (index + 1) % _values.length;
     return next;
   }
 
   int nextInt(int limit) => _next % limit;
 
   double nextDouble() => _next / 256.0;
 
   bool nextBool() => _next.isEven;
 }