Don't emit empty command buffers in vulkan

This may just cause use to do unneed loading and storing of memory.

Bug: skia:
Change-Id: I3f23d91df95f6e79b834fbb595ad9e9fb4371f9a
Reviewed-on: https://skia-review.googlesource.com/114793
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
1 file changed