Add test for cloned border-radius.
This has already been working for some time, but there was no test
coverage.
Bug: 40415661
Change-Id: I5e172747d278e66019414285e99b2c9b3578334d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5797055
Reviewed-by: Ian Kilpatrick ikilpatrick@chromium.org
Commit-Queue: Morten Stenshorne mstensho@chromium.org
Cr-Commit-Position: refs/heads/main@{#1344190}