Should unify EXT_platform_device and MESA_platform_surfaceless
These are, functionally, virtually identical. The only difference is that device requires you to specify an
EGLDeviceEXT, and surfaceless requires that you don't. We're the ones who define what surfaceless means, though, and we could quite reasonably extend it to allow specifying a device, with
NULL) falling through to the current "just pick something" behavior.