Fix @page outline.
Although page border boxes are anonymous blocks, there's nothing special
about their outlines in that regard.
Bug: 40286153
Change-Id: I072cdf1e775b14bd9fe8c2aa381e4dad2e277881
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5587875
Commit-Queue: Morten Stenshorne mstensho@chromium.org
Reviewed-by: Ian Kilpatrick ikilpatrick@chromium.org
Cr-Commit-Position: refs/heads/main@{#1309564}