It isn't Fission-compatible, and isn't likely to work with autofocus elements in OOP frames.

Do we actually allow autofocus in cross-origin iframes? How much do we care?

Tracking for Fission M7 Beta until we decide whether this needs to block shipping Fission.

Henri, is this critical for blocking Fission Nightly or Fission Beta?

I don't have actual evidence of use cases, but my guess is that this isn't critical or blocking (in fact, I think explicitly not allowing this might be a valid outcome).

The issue is in GetInProcessTop usage in TriggerAutoFocus and nsAutoFocusEvent. Henri said this isn't disastrous and can be dealt with later so moving to MVP.

I think this is INVALID/WONTFIX, we already don't trigger autofocus for cross-origin iframes even without fission: https://searchfox.org/mozilla-central/rev/919f7400e2e12bc963ee2ae8400ef961972c3059/dom/base/BindContext.cpp#24

But please reopen if I somehow got that wrong.