Add WebDX feature mapping for outline.
Change-Id: Ide8098f44647bcb4479bccc30cb65a58bd53f987
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5998678
Reviewed-by: Rune Lillesveen futhark@chromium.org
Reviewed-by: Shunya Shishido sisidovski@chromium.org
Commit-Queue: Steinar H Gunderson sesse@chromium.org
Cr-Commit-Position: refs/heads/main@{#1380282}