The Tor Browser / file revision

 // getVariable works on a heavyweight environment after control leaves its scope.

 var g = newGlobal();

 var dbg = Debugger(g);

 var envs = [];

 dbg.onDebuggerStatement = function (frame) {

     envs.push(frame.environment);

 };

 g.eval("var f;\n" +

        "for (var x = 0; x < 3; x++) {\n" +

        "    (function (x) {\n" +

        "        for (var y = 0; y < 3; y++) {\n" +

        "            (function (z) {\n" +

        "                eval(z); // force heavyweight\n" +

        "                debugger;\n" +

        "            })(x + y);\n" +

        "        }\n" +

        "    })(x);\n" +

        "}");

 var i = 0;

 for (var x = 0; x < 3; x++) {

     for (var y = 0; y < 3; y++) {

         var e = envs[i++];

         assertEq(e.getVariable("z"), x + y);

     }

 }