Assign unique per-pixel device coordinates in SkVM instead of all-zero.

If the device coordinates are constant across every lane, debug traces
can't generate reasonable results. If nothing actually uses the device
coordinates, the extra opcodes should DCE away.

Change-Id: Ic08a490a692e9c0bdd94f351193bc590d6540ded
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/473136
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
1 file changed