Refactor vk::Buffer memory allocation. Add the code that finds the right memory information into a shared location. This will allow it to be reused with other points in the code. BUG=angleproject:2167 Change-Id: I72d0522e134666d0a00921cb5ef6bc093473afdf Reviewed-on: https://chromium-review.googlesource.com/717189 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>