Vulkan: Prefer aggregate barriers on SwiftShader SwiftShader is not currently sensitivel to stage masks, so aggregating barriers leads to more efficient rendering. Bug: angleproject:4633 Change-Id: I262d1e98d4b08a1ca134a1c5c64ae964ceb6cd16 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3279020 Reviewed-by: Alexis Hétu <sugoi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>