Vulkan: Insert a barrier after buffer copy According to the spec(section 18.1), all copy commands are treated as transfer operations for the purposes of synchronization barriers. Some tests are flaky on Intel platform without such barriers. Bug: angleproject:2663 Bug: angleproject:2664 Change-Id: Ic8bc9a0eb000670342c0df0449257324f04ad1f8 Reviewed-on: https://chromium-review.googlesource.com/1124103 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>