The patch adds tests to verify that an occlusion query correctly tracks
whether any fragments pass the depth test for any of the views as
according to the ANGLE_multiview extension.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: Ia85bac4935192554a337c27fad110fbb7f56cf8a
Reviewed-on: https://chromium-review.googlesource.com/609961
Commit-Queue: Martin Radev <mradev@nvidia.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>