This is a smallest-change migration:
• The yield type is a dummy int. Nothing currently yields.
• There's no handling of coroutine resumes.

Bug: b/131672705
Change-Id: I238b1fa65c62ded7148816d87000103245373e33
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/30849
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>