Fix issue where command buffer was skipped if drawing a single drawable

When drawing a drawable in Vulkan, we didn't dirty the |fIsEmpty| flag
on the command buffer. This means that if the drawable was the only
output to the CB, it would not be submitted.

Change-Id: Id01a04d6423b64f1fe7a24065d5139184b132e77
Reviewed-on: https://skia-review.googlesource.com/c/190560
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Eric Karl <ericrk@chromium.org>
1 file changed