Interaction with user prompts

[beaufortfrancois]

What happens if there's an ongoing user prompt from the iframe? Does it get killed?

[yoavweiss]

We (for some value of "we") tried to kill user prompts from 3P iframes a few years back and it didn't take, but maybe we can at least say that a persistent-iframe can't fire user prompts at all?

/cc @estark37