My ECMAScript 7 wishlist

[André Bargull]

> that `has:()=>true` breaks with features detections that are meant to be
> less obtrusive than getters ... i.e. `'geolocation' in navigator` or
> `'innerHTML' in genericNode` and all others that are not supposed to pass
> through a potentially expensive getter to retrieve a feature detection
> purpose info.
>
> Long story short that NoSuchProperty is obtrusive in an upside-down way ...
> I personally would not use that and would not expect that anywhere

The 'has' handler is required to work around a Firefox limitation. A 
compliant ES6 implementation only needs the 'get' handler.

Related bug reports:
https://bugzilla.mozilla.org/show_bug.cgi?id=914314
https://bugzilla.mozilla.org/show_bug.cgi?id=1009199