anchor.diff:  
   @patch
   class Random {
  -  static Random _secureRandom;
  +  static Random? _secureRandom;
   
     @patch
  -  factory Random([int seed]) =>
  +  factory Random([int? seed]) =>
         (seed == null) ? const _JSRandom() : new _Random(seed);
   
     @patch
  
positive.code:         // Max is power of 2.
          return random & (max - 1);
        }
        int result = random.remainder(max);
        // Ensure results have equal probability by rejecting values in the
        // last range of k*max .. 256**byteCount.
        // TODO: Consider picking a higher byte count if the last range is a
  
negative.code: // 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.
  
  // Patch file for dart:math library.
  import 'dart:_foreign_helper' show JS;
  