Implement rowspan=0

Bug: 180722
Change-Id: I187155b0076d8f4e7d9e7c9e7b80d9686a12ad2c
Reviewed-on: https://chromium-review.googlesource.com/808929
Commit-Queue: Robert Hogan <robhogan@gmail.com>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523553}
27 files changed