Fix spec violations in methods of Number.prototype.

test/mjsunit/regress/regress-crbug-18639.js

Index: test/mjsunit/regress/regress-crbug-18639.js
diff --git a/test/mjsunit/regress/regress-crbug-18639.js b/test/mjsunit/regress/regress-crbug-18639.js
index 23e225a4f455067357fa2f71b9efc3cfd9048914..4f4bb7c796bcbf4f0144744d6535a9f0909f0318 100644
--- a/test/mjsunit/regress/regress-crbug-18639.js
+++ b/test/mjsunit/regress/regress-crbug-18639.js
@@ -27,8 +27,12 @@
 
 // See http://crbug.com/18639
 
-toString = toString;
-__defineGetter__("z", (0).toLocaleString);
-z;
-z;
-((0).toLocaleString)();
+try {
+  toString = toString;
+  __defineGetter__("z", (0).toLocaleString);
+  z;
+  z;
+  ((0).toLocaleString)();
+} catch (e) {
+  assertInstanceof(e, TypeError);
+}