Number.prototype.toLocaleString([locales[, options]]) extern

There is an extern for `Object.prototype.toLocaleString()` in [es3.js](/google/closure-compiler/blob/master/externs/es3.js).

Should there also be an overriding extern for [`Number.prototype.toLocaleString()`](//developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number/toLocaleString) with its two optional parameters, perhaps in one of either the ES5 or (more likely) ES6 extern files? Or was this intentionally left out?

Right now, passing anything to the method gives me a warning based on `Object.prototype.toLocaleString()`, which expects exactly zero arguments.
I considered it, but I wasn't sure if it would be better to instead reuse the record type defined in [intl.js](/google/closure-compiler/blob/85e803/externs/intl.js#L94-L102), maybe turn it into a real `@typedef` and use it in both places (and others, should they arise)? Then I just got lazy and thought, "eh, this is probably good enough." :neutral_face:

Let me know if there's a preference or precedent.