From @matmarex's comment on https://gerrit.wikimedia.org/r/#/c/283652/
- No changes to TextInputWidget (except maybe a deprecation warning?), introduce SearchInputWidget that just does calls parent constructor with { type: 'search' } – this would be just a deprecation, code depending on OOjs UI could be updated to use new SearchInputWidget
- Revert changes from step 1 and do this change – this would be a breaking change, but hopefully all code was already updated by this point