[PATCH 00/18] Misc exposure/validation cleanups, v2

[Adam Jackson]

This series no longer has the spontaneous combustion removal.  5 and 6 are
instead just propagating through the 'exposures = prgn' bit of the logic.
It also no longer has the doVisibilityNotify refactor, since in 10 we
discover that the second path can't actually get hit so there's no reason
to factor it out.

The rest from 11 to 18 are new, and hopefully boringly correct.

- ajax