GitLab

When TestPageFlip, choose the FourCC format that takes opacity into
consideration.

BUG=983937
TEST=GPU doesn't crash anymore on Kefka

Change-Id: I72af7f1755c9cd9c4464246fc73d38adbec57b25
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724558Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Commit-Queue: Mark Yacoub <markyacoub@google.com>
Auto-Submit: Mark Yacoub <markyacoub@google.com>
Cr-Commit-Position: refs/heads/master@{#682848}