Aside from more SPIR-V using OpConstantNull, this is a no-op change.
By refactoring these methods, they're easier to read, and contain less
lambda-heavy code.
Change-Id: I89c26b2b9f1cd0785d86fb3293f7cfda550bef2e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/94331
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
5041480715