Steps to replicate the issue (include links if applicable):
As discussed in zhwiki (link), the dropdown options (message key protect-expiry-options) in action=protect are displayed in zh-hans for sysops using zh-hant variants. This happens when $wgLanguageCode = "zh", which fallbacks to zh-hans.
What happens?:
ProtectionForm.php uses Message::inContentLanguage to access that translation string. It has been accessed this way since it was split from ipboptions in rMW7049385. ipboptions has no longer been exclusively rendered in the content language after rMWad0e525.
What should have happened instead?:
Adding it to $wgForceUIMsgAsContentMsg will cause the dropdown menu to be displayed in zh-hant correctly. I am not sure if just removing ->inContentLanguage() on that line suffice.
Software version: 1.45.0-wmf.12