We already had to introduce TypeAlias to allow types to be const.
With TypeAlias, there is no need for types to be declarable themselves.

Change-Id: Ia718482f6c121b5316aca819368e6d048283e5e8
Reviewed-on: https://chromium-review.googlesource.com/1068734
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53282}