Flex: Don't make extra room for box decorations if not cloning.
When adding support for box-decoration-break:clone to flex containers,
we mistakenly ended up making additional room for box decorations to
fragmented flex items, even if they are not to be cloned.
Bug: 359296620
Change-Id: I0d7f3ed716f689569d03ddd3a4c266aaa9ff4a4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5789284
Reviewed-by: Alison Maher almaher@microsoft.com
Commit-Queue: Morten Stenshorne mstensho@chromium.org
Cr-Commit-Position: refs/heads/main@{#1342902}