GitLab

* Allow string whenever a property is text, Thing, or Enum type.
* Allow URL whenever a property is Thing or Enum type, /as long as/ the
  URL is a schema.org ID of an appropriate thing or enum.

https://schema.org/docs/gs.html#schemaorg_expected

Change-Id: I72edef99f705c64838f09829de6c34058b10b860
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2144401Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Sam Bowen <sgbowen@google.com>
Cr-Commit-Position: refs/heads/master@{#758367}