Revert of change SkDraw and all Blitters to use pixmap instead of bitmap (patchset #6 id:100001 of https://codereview.chromium.org/1148793007/)

Reason for revert:
speculative revert to try to unblock DEPS roll

Original issue's description:
> change SkDraw and all Blitters to use pixmap instead of bitmap
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/c31af44336f5eb4a50e83e76e51962d46c3ed458

TBR=scroggo@google.com,jvanverth@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1164373003
29 files changed