Tried both Chrome Dev and Canary on iOS 12.

Loaded united.com.
Tap on the "people" icon on the top right.

Expected:
Password autofill.

Observed:
"MileagePlus number" is always empty. There are "*****" in the password field for couple of second. Then they are gone.

Tap on "MileagePlus number".
The keyboard is up and it shows my saved account number with password as "****". Tap on it to trigger autofill.

Expected:
Autofill to the two fields.

Observed:
Nothing is filled