Add WebDX feature mapping for marker.
Change-Id: I0ef53f57813a94064c9e996a06f9b15bae79f4ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6001397
Commit-Queue: Steinar H Gunderson sesse@chromium.org
Reviewed-by: Shunya Shishido sisidovski@chromium.org
Reviewed-by: Rune Lillesveen futhark@chromium.org
Cr-Commit-Position: refs/heads/main@{#1380341}