Add EVENT0 markers for why we call vkAcquireNextImage This will help when looking at AGI system traces. Bug: angleproject:6696 Change-Id: Ic4b06f1a1ec155076cfcb47299afe451cd325327 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3283428 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>