Vulkan: Internal Compute support While this is not exposed to the front end yet, this commit adds support for creating Compute pipelines for internal usage. Bug: angleproject:2959 Change-Id: I976eae1ce0f736c257b7b4ae0d1c3b2d9f4da5bb Reviewed-on: https://chromium-review.googlesource.com/c/1333972 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>