Revert "Convert the CPU mask case to use prepareForDrawing"

This reverts commit c48879ed404c619adb59d5a1f10855042bf754b3.

Reason for revert: Regresses on fuzzer because it doesn't handle glyphs wider than 32K correctly

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>

TBR=bungeman@google.com,herb@google.com

Change-Id: I046f24fd541dd121b8fa65ff5811c3055a28215d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208041
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Herb Derby <herb@google.com>