Array.prototype.contains

[Domenic Denicola]

> That would not allow us to kill DOMStringList.

Can we get more background on DOMStringList? It seems unlikely that you could get away with replacing a string-only type, which, from the specs I can find, seems to be immutable and have an additional index() method, with an actual mutable any-type-containing array.

It's not in http://dom.spec.whatwg.org (except as "don't implement this") and https://developer.mozilla.org/en-US/docs/Web/API/DOMStringList implies it's not implemented in Mozilla, and only used by an obscure property.