Add more tests for dangling markup mitigation

Adding more test per request[1].

[1] https://github.com/whatwg/html/pull/10022#pullrequestreview-1841928335

Change-Id: I7d4d3494fa3aa0ac41c48727c2f866ccf3f016d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5278680
Reviewed-by: Jonathan Hao <phao@chromium.org>
Reviewed-by: Yifan Luo <lyf@chromium.org>
Auto-Submit: Jun Kokatsu <jkokatsu@google.com>
Commit-Queue: Jun Kokatsu <jkokatsu@google.com>
Cr-Commit-Position: refs/heads/main@{#1261160}