create() is currently just a simple forwarder to std::make_unique<>, but
will be later replaced with a function that returns a raw pointer,
and owned by the context.
Bug: tint:322
Change-Id: I630ce57017fe84b5d00e9bd74902f47547a13f3a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/32669
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>