Add attribute reflection behavior for dialog closedBy [2/N]
This implements reflection of closedBy including the "limited to
known values" behavior.
See spec PR for details:
whatwg/html#10737
Bug: 376516550
Change-Id: Iddefd573fe19fd39f4b3aebe13390235fea969b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5988652
Commit-Queue: Mason Freed masonf@chromium.org
Reviewed-by: David Baron dbaron@chromium.org
Commit-Queue: David Baron dbaron@chromium.org
Auto-Submit: Mason Freed masonf@chromium.org
Cr-Commit-Position: refs/heads/main@{#1379228}