OptionalreadRead the persisted active-flavor pointer back, if the host can.
Optional. Supplying it lets the switcher tell a refused pointer write that would have changed nothing from one that would have: without it, every refusal fails the switch, which is the behaviour a host that does not supply it already had.
Load + activate an extension that's being enabled. Returns false on failure.
Persist the active-flavor pointer.
Set the enabled flag on an installed extension.
Stop any running activation for an extension that's being disabled.