Chrome Version: 71.0.3556.0
OS: 11042.0.0

Vietnamese VNI currently lacks the standard transform rule whereby typing "0" triggers tone mark erasure on an applicable preceding letter, if there's currently a tone mark diacritic above it.

Which letter exactly to apply the erasure depends on whether strict or flexible trigger mode is active. This should only affect tone-mark diacritics, leaving letter-modifier diacritics intact.

Non-exhaustive examples:
- type "ca10" -> expect "ca", currently get "cá0"
- type "da1ng0" -> expect "dang", currently get "dáng0"

NOTE: When flexible trigger is active, this should work correctly for *all* cases as per Vietnamese orthography, with regard to diacritic placement and syllable structure, not just the minimal simplistic examples above. The VNI rule itself, if implemented correctly as such, is linguistically sound and thus consistent and reliable.