CSS: WPTs for dominant-baseline parsing

dominant-baseline is specified to accept
auto | text-bottom | alphabetic | ideographic | middle | central
| mathematical | hanging | text-top

Blink hasn't implemented support for text-bottom or text-top.

https://drafts.csswg.org/css-inline-3/#dominant-baseline-property

Change-Id: I956027066788415063ee0d6b9867af458da365cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1728890
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682671}