Using a depth buffer format requires that the DSV and RTV have equal
quality levels; otherwise, the bound render target will discard writes.

BUG=angleproject:1917

Change-Id: Ife25b0a8958fa2b31b43a0d877d27e440916a9bf
Reviewed-on: https://chromium-review.googlesource.com/560716Reviewed-by: Bryan Bernhart <bryan.bernhart@intel.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>