align-content for blocks: Fix an issue with scrollable containers

We should apply "safe" if <overflow-position> is not specified and the
container is scrollable.

Bug: 331454369
Change-Id: I63cc9954ecbd8013e46b4f1f0c0eb2d9f19fe95e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5400870


Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1280526}