Better optimize our use of memory barriers in vulkan.

Bug: skia:
Change-Id: I519c4d0e2bcf89492595fb63bbe354e4a747547e
Reviewed-on: https://skia-review.googlesource.com/c/160769
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
7 files changed