The Tor Browser / file revision

 var foo;

 function gen() {

     var x = 0;

     foo = function() { return x++; }

     for (var i = 0; i < 10; ++i)

         yield x++;

 }

 var j = 0;

 for (i in gen())

     assertEq(i, j++);

 // now mess up the stack

 function f1(x) {

     var a, b, c, d, e, f, g;

     return x <= 0 ? 0 : f1(x-1);

 }

 f1(10);

 function f2(x) {

     var a = x, b = x;

     return x <= 0 ? 0 : f2(x-1);

 }

 f2(10);

 // now observe gen's call object (which should have been put)

 gc();

 assertEq(foo(), 10);

 gc();

 assertEq(foo(), 11);

 gc();

 assertEq(foo(), 12);

 reportCompare(true,true);