Depends on D19924. Ref T11351. Like in D19924, apply these transactions by accepting PHIDs instead of objects so we don't need to juggle the Image objects down to PHIDs in applyInitialEffects.
(Validation is a little light here for now, but only first-party code can reach this, and you can't violate policies or do anything truly bad even if you could pick values to feed in here.)