[css-tables] Test for relpos row establishing a cb

Blink's recent attempt to implement relative positioning for table rows
broke position of absolute position descendents. This is a test to
ensure it doesn't happen again.

Bug: 417223
Change-Id: I9c8d0d54c48d4f4426d3ad71dff562b67396f68e
Reviewed-on: https://chromium-review.googlesource.com/907754
Commit-Queue: David Grogan <dgrogan@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535891}
2 files changed