WebDX mapping for white-space-collapse

Change-Id: Ie5e475520145b62e1d9273d56c02c74e1435ebfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5991431


Reviewed-by: Steinar H Gunderson <sesse@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Noam Rosenthal <nrosenthal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1378955}