ScopeStack is not needed here - the resolver already provides variable scoping with the sem::Variables.
Re-purpose scope_stack_ for a stack of Scope, which now holds the type constructor -> SPIR-V ID map.
This map needs to be per-scope, to fix issues like crbug.com/tint/1520
Fixed: tint:1520
Change-Id: Ifa7749338abf63652a1369e76cf5400be1c37298
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/88301
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Ben Clayton