remove dead code from old drawimage virtuals

Bug: skia:7650
Change-Id: Ie6bce2130519655645b7c5602d364cd0e1d6fdf3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/356358
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
17 files changed