In Firefox we disabled the capability for a third-party to prompt for the persistent storage permission.

Doing this helps with https://privacycg.github.io/storage-partitioning/ and also helps reduce the number of prompts where the third-party is shown.

(Delegation through the allow="" attribute does not work, unless we reinterpret that as the first-party sharing its storage area, but that should probably be its own issue if there's interest in that kind of thing.)

This would be easy to add by adding a check for origin != top-level origin in the relevant places. Is there interest from Chrome?

cc @inexorabletash