Add dialog light dismiss behavior (the actual click outside part) 5/5
This adds to the prior CLs to actually allow "click outside" to
function as a light dismiss trigger.
See spec PR for details:
whatwg/html#10737
Bug: 376516550
Change-Id: I62158e092de9acac182777f2ad9864e818128907
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6013845
Commit-Queue: David Baron dbaron@chromium.org
Reviewed-by: David Baron dbaron@chromium.org
Auto-Submit: Mason Freed masonf@chromium.org
Cr-Commit-Position: refs/heads/main@{#1383792}