I think I'd double, but I'd like it to mean 'Partner, you decide whether you leave it or go on'. I already bid 3♠ so partner should support me with 3 or 4 spades, since he didn't and didn't double himself he might have some hearts and maybe both minors and 4♥x could be our best contract. Another question is whether his double would have been for penalties, in which case his hearts wouldn't be very important and a game in a minor or 4♠ might be better. Also, is his Pass forcing? I think it sort of is.