Make xformer class for SkCSXCanvas, use for draw loopers

Fixes draw looper gms in gbr-8888 config.

Bug: skia:
Change-Id: I0a9306cc0523c82f2ad9516752d79c1d86b1e295
Reviewed-on: https://skia-review.googlesource.com/10644
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
9 files changed