remove unneeded bitmapprovider abstraction

Change-Id: Idd413389bb0828a6fc73b7285b4ed7b6fe48af6f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/231638
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
13 files changed