Fix up GPUDDLSink for Vulkan

Change-Id: If38afff3d07f51fd0f5a989c2f59e3c788086f8b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/284099
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed