Make the regression test for bug 559438 less confusing. r=peterv.

js/src/tests/js1_8_5/regress/regress-559438.js

@@ -6,5 +6,5 @@
 
 function f(x) { return 1 + "" + (x + 1); }
 reportCompare("12", f(1), "");
-var g = eval(String(f));
-reportCompare("12", f(1), "");
+var g = eval("(" + f + ")");
+reportCompare("12", g(1), "");