- Extend the coin test for slightly different scenarios.

runtime/lib/math_patch.dart

Index: runtime/lib/math_patch.dart
===================================================================
--- runtime/lib/math_patch.dart	(revision 23308)
+++ runtime/lib/math_patch.dart	(working copy)
@@ -49,7 +49,11 @@
     do {
       seed = (seed + 0x5A17) & _Random._MASK_64;
     } while (seed == 0);
-    return new _Random._internal(seed);
+    // Crank a couple of times to distribute the seed bits a bit further.
+    return new _Random._internal(seed).._nextState()
+                                      .._nextState()
+                                      .._nextState()
+                                      .._nextState();
   }
 }