- Preliminary change for gl_PointCoords fix for Vulkan.

Bug: angleproject:2673
Change-Id: Ie43e8aeccf75a8daa4a137b98292d848522ea2f0
Reviewed-on: https://chromium-review.googlesource.com/1134877Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Luc Ferron <lucferron@chromium.org>