The patch adds the new end-points and tokens introduced
by ANGLE_multiview without implementing them.

BUG=angleproject:2062

Change-Id: I9be175263ab54b4f6d7537f05505b87ad763ee2d
Reviewed-on: https://chromium-review.googlesource.com/570051Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>