The patch adds a sample which makes use of the ANGLE_multiview
extension to draw the same scene to two views each having its
own camera matrix.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: I4b765a189047bf219a05e98b032ad95efbb36905
Reviewed-on: https://chromium-review.googlesource.com/655166
Commit-Queue: Martin Radev <mradev@nvidia.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>