Add support for EGL_MESA_platfrom_surfaceless extension This adds support for the EGL_PLATFORM_SURFACELESS_MESA platform type to allow applications to obtain an EGLDisplay that's independent of any native windowing systems. This will be used in Ozone/Wayland to create surfaceless EGLDisplays. Bug: angleproject:8331 Change-Id: If2ae7a811cfa63ab9f49d54d78f5a3782c8c2fed Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4749337 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>