The motion tile phase is a one-dimensional shift, applied to every other
row or column (based on a selector property).
Implement using a masking shader (covering the static rows/cols),
and blend mode shader composition (srcIn for static/pass-through
rows/cols, and srcOut for phased rows/cols).
TBR=
Change-Id: I336c150e5d4900962dc2de801a4e1572cf4b5d59
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/221339
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
