[Selection API] Add DOM mutation removal test
Add nested shadow host case.
Change-Id: Iebf8f6dfc52b7c5274b29946b6389f7ad717759f
Bug: 40286116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6026955
Auto-Submit: Di Zhang dizhangg@chromium.org
Reviewed-by: Siye Liu siliu@microsoft.com
Commit-Queue: Siye Liu siliu@microsoft.com
Cr-Commit-Position: refs/heads/main@{#1384420}