more cleanup after removing volatile from bitmap

Change-Id: I3d7b2f59a5657640c3d60f5a2f6e1277d7593096
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302038
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
9 files changed