These methods produce `let` declarations.
With creation-time expressions, we'll need to add `const` declarations.
Note that module-scope `let` declarations have been removed in the spec (for `const`). ProgramBuilder::GlobalConst() has not been renamed, although it still currently produces 'let' declarations.
Bug: tint:1504
Change-Id: I34f6d62236f0572163fc9c2d8fddfe4503817422
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/88305
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>