Handle cloned background images correctly.
The start offset into the background image will be the same at every
fragment if box-decoration-break is 'clone'.
Bug: 40415661
Change-Id: I1619d4727e2f24d9b9d0cb6a5c1d13209834f40a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5799867
Reviewed-by: Ian Kilpatrick ikilpatrick@chromium.org
Reviewed-by: Xianzhu Wang wangxianzhu@chromium.org
Commit-Queue: Morten Stenshorne mstensho@chromium.org
Cr-Commit-Position: refs/heads/main@{#1344260}