This was introduced in:
commit 010d16f647
Author: Robert Bragg <robert@linux.intel.com>
Date: Tue Mar 6 03:21:30 2012 +0000
Adds initial GLES2 integration support
This makes it possible to integrate existing GLES2 code with
applications using Cogl as the rendering api.
That's maybe a reasonable thing for a standalone cogl to want, but our
cogl has only one consumer. So if we want additional rendering out of
our cogl layer, it makes more sense to just add that to cogl rather than
support clutter or mutter or the javascript bindings creating their own
GLES contexts.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/500
7e8a864992