Remove dead code (and dead subclass)

note: our min picture-version dates from 2020
Change-Id: I5b9d2e8a13afd16fe5b3ae88f9747f0da4382d29
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/428196
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed