Allow including of vulkan.h as a required public api when using vulkan.

Bug: skia:
Change-Id: I3ac382edc12144dcda9ef168f752b14878e0e5ac
Reviewed-on: https://skia-review.googlesource.com/13262
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
2 files changed