This bug is a continuation of bug 1410734. There, we're testing that L20n infra handles language fallbacking correctly, but we're operating with the limited set of requestedLocales. In order to open that up and allow for requested locales list to handle longer fallback chains (bug 1414390), we need to ensure that L20n infra handles such chains well. This bug should cover scenarios: Choice A): Nightly en-US `or` Nightly ab-CD w/out ftl `or` Nightly ab-CD w/ ftl Choice B): No langpack `or` ef-GH langpack w/out ftl `or` ef-GH langpack w/ ftl Choice C): requestedLocales is ['ab-CD', 'ef-GH', 'en-US'] `or` ['ef-GH', 'ab-CD', 'en-US']

With bug 1414390 being close to ready, I'll start testing scenarios involving multiple fallback locales.

With the patch in bug 1422997, the test matrix is now green: https://docs.google.com/spreadsheets/d/1kywdUDSnGMTDHBNzAIkJ41M4NpS8iYBWAsJ6D0KPjJs/edit#gid=1162027777