STR

1. Visit http://example.com/ until it autofills
2. Type "ex" so that example.com/ autofills
3. Type another x (so that the input contains "exx")
4. Ctrl-Z to undo the extra x

At that point, example.com/ autofills again, which may be confusing or unexpected. We should consider prohibiting autofill on undo.

Editor's nsITransactionListener may be helpful for listening for undo: https://searchfox.org/mozilla-central/rev/dd7e27f4a805e4115d0dbee70e1220b23b23c567/editor/txmgr/nsITransactionListener.idl#55

See also bug 1541929, which ended up fixing a different problem. That bug added this test: https://searchfox.org/mozilla-central/rev/d302c3058330a57f238be4062fddea629311ce66/browser/components/urlbar/tests/browser/browser_autoFill_undo.js Which would need to be updated.

This is something we should consider after QB mvp, it's not strictly necessary for now and requires UX feedback. maybe we should make it just block quantumbar-input but not a blocker (I expect quantumber-autofill will be resolved once defects are resolved, ignoring enhancements)

Sounds good.