Better check for non-contiguous IFCs.

Finding a non-atomic inline fragment item inside a containing block fragment isn't enough to consider the inline formatting context to be contiguous. We need some actual content, such as an atomic inline or text.

In the test included there's a text node that occurs in the first and third column, but not in the second.

Bug: 1494201 Change-Id: Iaddcf3a200f5111f899ea1de28f75c049e0d9e58 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4958334 Commit-Queue: Morten Stenshorne mstensho@chromium.org Reviewed-by: Koji Ishii kojii@chromium.org Cr-Commit-Position: refs/heads/main@{#1212691}