Correct scroll snap area for fragmented blocks.
A DCHECK would fail if a node got block-fragmented, since we'd add the
LayoutBox for it multiple times. Only add the LayoutBox when at the last
fragment.
Secondly, calculate the correct bounding box for such blocks.
PhysicalBorderBoxRect() would give the rectangle in the stitched
coordinate system (where we pretend that nothing gets fragmented, but is
just laid out into one tall strip). Use QuadsInAncestor() instead.
Bug: 353898977
Change-Id: I94bd2f7f3d25a8f154e0f7fe7fc35373fbcf7449
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5854900
Commit-Queue: Morten Stenshorne mstensho@chromium.org
Reviewed-by: Ian Kilpatrick ikilpatrick@chromium.org
Cr-Commit-Position: refs/heads/main@{#1355444}