Reland "Convert the CPU mask case to use prepareForDrawing"

This is a reland of c48879ed404c619adb59d5a1f10855042bf754b3

BUG=952629

Original change's description:
> Convert the CPU mask case to use prepareForDrawing
>
> Change-Id: I3a36084544e12730f4815dbf5b6c78a1cd719f1b
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207761
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: Herb Derby <herb@google.com>

Change-Id: I382901e2a4cc186b206450cd4ae8058c6c0e2149
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208042
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
3 files changed