ObjectDumper.p.dump: use Array for visiting set
ObjectDumper.p.dump: use Array for visiting set

Since ObjectDumper.prototype.dump's visting set for is never going to be especially big, and we're constantly adding and removing items, use an Array instead of a Set.

google/CodeCity,NeilFraser/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity