css-flexbox: Add tests for sideways-* containers
The tests are based on existing flexbox-writing-mode-*.html.
Bug: crbug.com/40501131
Change-Id: I8fa9e2dcf04ceb01f93801d2570af2be76f21eae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5726638
Commit-Queue: Kent Tamura tkent@chromium.org
Reviewed-by: Ian Kilpatrick ikilpatrick@chromium.org
Cr-Commit-Position: refs/heads/main@{#1331426}