This is required to generate valid MSL code, and will soon be
validated by Tint too.
Change-Id: I4c5f5c4ecb1c91131c934de1132217d9f6be1f8e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53420
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>