Vulkan: Work around Qualcomm imprecision with dithering On qualcomm, sometimes the output is ceil()ed instead of round()ed. With ditering emulation affecting values, some dEQP tests fail due to the excessive change in value when dithering bumps the value slightly over to the next quantum. In this change, a workaround is added to round() the value before outputting it. Bug: angleproject:6953 Change-Id: Iae7df5ca20055b4db3185c6153f3c0bf4ba07f68 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3611064 Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>