All the fragment_ops.depth and the fragment_ops.depth tests in dEQP are
now working, but not the fragment_ops.depth_stencil. Still debugging
these separately and will come up with a fix for them in another
commit.

Bug: angleproject:2443

Change-Id: I84c3a22f612fb6dcf30598434f96c2100fd29f9c
Reviewed-on: https://chromium-review.googlesource.com/993654
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>