GitLab

Updates the Anchors API to align with changes proposed in the
immersive-web CG repository:
https://github.com/immersive-web/anchors/pull/29

Change-Id: I1ebc332c1f4b00c8912bf132f924ffa3f383dfa8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2051394Reviewed-by: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Piotr Bialecki <bialpio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#740830}