Vulkan: acquire swapchain image should use COLOR_ATTACHMENT_OUTPUT_BIT The mAcquireImageSemaphore is for achieving the maximum overlap between display engine and rendering engine. We should only need to block when we write to the swapchain image. Work that doesn't touch the visible buffer can proceed. Bug: b/157916459 Change-Id: Ic9a9a1f2a7648ef7f50f99578a0f0d674ae5e66c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2223826 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>