Make List.shuffle take an optional Random object to use.

sdk/lib/_collection_dev/iterable.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.
 
 part of dart._collection.dev;
 
 
 // This is a hack to make @deprecated work in dart:io. Don't remove or use this,
 // unless coordinated with either me or the core library team. Thanks!
 // TODO(ajohnsen): Remove at the 11th of August 2013.
@@ skipping 940 matching lines @@
 
   static Iterable reversedList(List list) {
     return new ReversedListIterable(list);
   }
 
   static void sortList(List list, int compare(a, b)) {
     if (compare == null) compare = Comparable.compare;
     Sort.sort(list, compare);
   }
 
-  static void shuffleList(List list) {
-    Random random = new Random();
+  static void shuffleList(List list, Random random) {
+    if (random == null) random = new Random();
     int length = list.length;
     while (length > 1) {
       int pos = random.nextInt(length);
       length -= 1;
       var tmp = list[length];
       list[length] = list[pos];
       list[pos] = tmp;
     }
   }
 
@@ skipping 121 matching lines @@
 
   static Set setDifference(Set set, Set other, Set result) {
     for (var element in set) {
       if (!other.contains(element)) {
         result.add(element);
       }
     }
     return result;
   }
 }