The enums introduced by the ANGLE_multiview extension are changed
to use the values reserved specifically for ANGLE.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: Ib668f2e0e9022442a432b1a04050aeb2ff82a3d1
Reviewed-on: https://chromium-review.googlesource.com/654864Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Martin Radev <mradev@nvidia.com>