The Tor Browser / file revision

 var otherGlobalSameCompartment = newGlobal("same-compartment");

 eval = otherGlobalSameCompartment.eval;

 doesNotNeedParens(1, "if (xx) { }");

 needParens(2, "if (1, xx) { }");

 function doesNotNeedParens(section, pat) {

     try {

         f = new Function

     } catch (e) {}

     roundTripTest(section, f)

 }

 function needParens(section, pat, exp) {

     var f, ft;

     roundTripTest(section, f, exp)

 }

 function roundTripTest(section, f, exp) {

     uf = "" + f

     var euf;

     try {

       euf = eval("(" + uf + ")");

     } catch (e) { }

     + euf

 }