- Do not rely on time to seed the default PRNG.

runtime/lib/math_patch.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.
 
 import "dart:typed_data";
 
 // A VM patch of the dart:math library.
 
 // If [x] is an [int] and [exponent] is a non-negative [int], the result is
 // an [int], otherwise the result is a [double].
@@ skipping 136 matching lines @@
   // Constants used by the algorithm or masking.
   static const _MASK_32 = (1 << 32) - 1;
   static const _MASK_64 = (1 << 64) - 1;
   static const _POW2_32 = 1 << 32;
   static const _POW2_53_D = 1.0 * (1 << 53);
   static const _POW2_27_D = 1.0 * (1 << 27);
 
   static const _A = 0xffffda61;
 
   // Use a singleton Random object to get a new seed if no seed was passed.
-  static var _prng = null;
+  static var _prng = new Random(_initialSeed());

[siva, 2014/03/17 17:46:02]

This can potentially result in an overflow error when the flag
--throw_on_javascript_int_overflow flag is used.

+
+  static int _initialSeed() native "Random_initialSeed";
 
   static int _nextSeed() {
-    if (_prng == null) {
-      // TODO(iposva): Use system to get a random seed.
-      _prng = new Random(new DateTime.now().millisecondsSinceEpoch);
-    }
     // Trigger the PRNG once to change the internal state.
     _prng._nextState();
     return _prng._state[kSTATE_LO];
   }
 }