Rewrite EGL_ANGLE_platform_angle_context_virtualization to
EGL_ANGLE_context_virtualization, changing the context virtualization
parameter to an identifier for what virtualization group the frontend
context should be added to.
This allows ANGLE's GL backend to be used by multiple threads if the
user creates contexts with different virtualization groups.
Bug: angleproject:6406
Change-Id: I7414d4705ce10bdf63a9b824043d5dd040dad875
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3169193
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Geoff Lang