The now-removed SPIRV-Cross path used to always do this, and the
pure Tint-only path never actually validated the SPIRV. Tint
does not run SPIRV-Tools validation on its output, so add in
validation to ensure we don't pass invalid SPIRV to the driver.
The validation can probably eventually be removed when we're more
confident that Tint's SPIRV output is always correct.
Also include various cleanups for old / unused code.
Bug: dawn:1036
Change-Id: Iaab037518965e52edbd1829f6ab6ba2af0e70143
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/61589
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Jiawei Shao <jiawei.shao@intel.com>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Auto-Submit: Austin Eng <enga@chromium.org>
