Let random seed be a property

lib/random/random.js

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var random = { // eslint-disable-line no-unused-vars
+  seed: null,
   twister: null,
 
   /**
@@ -11,10 +12,10 @@ var random = { // eslint-disable-line no-unused-vars
    */
   init: function (seed) {
     if (seed === null || seed === undefined) {
-      seed = new Date().getTime()
+      this.seed = new Date().getTime()
     }
     this.twister = new MersenneTwister()
-    this.twister.seed(seed)
+    this.twister.seed(this.seed)
   },
   number: function (limit) {
     // Returns an integer in [0, limit). Uniform distribution.