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: I69487200d9595f3176615ee1edf81da9fe1f5abc
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/32670
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>