Add a 'secure' constructor to Random in dart:math returning a cryptographically

sdk/lib/_internal/js_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.
 
 // Patch file for dart:math library.
 import 'dart:_foreign_helper' show JS;
 import 'dart:_js_helper' show patch, checkNum;
 
 @patch
 double sqrt(num x)
@@ skipping 42 matching lines @@
   return JS('num', r'Math.pow(#, #)', x, exponent);
 }
 
 const int _POW2_32 = 0x100000000;
 
 @patch
 class Random {
   @patch
   factory Random([int seed]) =>
       (seed == null) ? const _JSRandom() : new _Random(seed);
+
+  @patch
+  factory Random.secure() {
+    throw new UnsupportedError("Unsupported secure random generator");

[Lasse Reichstein Nielsen, 2015/10/14 11:08:45]

No need to write "unsupported" in the message too, the error's toString prefixes
the message with "Unsupported operation: ".

[regis, 2015/10/14 20:22:35]

Done.
I used the message you suggested for the VM:
No source of cryptographically secure random numbers available.

+  }
 }
 
 class _JSRandom implements Random {
   // The Dart2JS implementation of Random doesn't use a seed.
   const _JSRandom();
 
   int nextInt(int max) {
     if (max <= 0 || max > _POW2_32) {
       throw new RangeError("max must be in range 0 < max ≤ 2^32, was $max");
     }
@@ skipping 156 matching lines @@
     _nextState();
     int bits27 = _lo & ((1 << 27) - 1);
     return (bits26 * _POW2_27_D + bits27) / _POW2_53_D;
   }
 
   bool nextBool() {
     _nextState();
     return (_lo & 1) == 0;
   }
 }