Storing the texture index in the lower bit of each texture coordinate
seems to have issues on certain iOS devices. Rather than do that, we
use the sign of the texture coordinate to act as our storage bit.
To manage encoding 0 we map [0, N] to [-1, -N-1] to represent a bit.
Change-Id: Ic588ee92cf858915a1833cf482d4b23bd11c1000
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263561
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
c8b2e61540