Improve performance of String.split for 1 and 0 character results.

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.
 
 // A VM patch of the dart:math library.
 patch num pow(num x, num exponent) {
   if (exponent is int) {
     return x.pow(exponent);
   }
   // Double.pow will call exponent.toDouble().
@@ skipping 33 matching lines @@
     do {
       seed = (seed + 0x5A17) & _Random._MASK_64;
     } while (seed == 0);
     return new _Random._internal(seed);
   }
 }
 
 
 class _Random implements Random {
   // Internal state of the random number generator.
-  var _state;
+  final _state = new List(2);
   static const kSTATE_LO = 0;
   static const kSTATE_HI = 1;
 
   _Random._internal(state) {
-    _state = new List(2);
     _state[kSTATE_LO] = state & _MASK_32;
     _state[kSTATE_HI] = state >> 32;
   }
 
   // The algorithm used here is Multiply with Carry (MWC) with a Base b = 2^32.
   // http://en.wikipedia.org/wiki/Multiply-with-carry
   // The constant A is selected from "Numerical Recipes 3rd Edition" p.348 B1.
   int _nextInt32() {
     var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64;
     _state[kSTATE_LO] = state & _MASK_32;
@@ skipping 41 matching lines @@
 
   static int _nextSeed() {
     if (_prng == null) {
       // TODO(iposva): Use system to get a random seed.
       _prng = new Random(new Date.now().millisecondsSinceEpoch);
     }
     // Trigger the PRNG once to change the internal state.
     return _prng._nextInt32();
   }
 }