Comment 3 for bug 1439829

Ok code is doing platform specific things (reading GRID_UNIT_PX, getting a shared gl context is very QPA plugin), so yeah the qpa name is a good way to distinguish them. Figuring out if it should GL or GLES really should be something Qt can communicate. We're exclusively using GLES for now, but desktop will gain GL support in time, so this fix isn't future-proof