merge_pr_51528

Column rule painting for wrapped columns.

Not perfect, but hopefully good enough until we get CSSGapDecoration
(which is also required for row rules).

Refactor BoxFragmentPainter::PaintColumnRules() to avoid duplicated
logic for horizontal and vertical writing mode, and add support for
multiple consecutive rows (without intervening spanners). Also paint
column rules in the row gaps.

Add some getters for start offsets and sizes to LogicalRect.
PhysicalRect already has them.

Bug: 403183884
Change-Id: Ic866f4ba242da796ecd3ead093accfcc71a3feb8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6382075
Commit-Queue: Morten Stenshorne [email protected]
Reviewed-by: Xianzhu Wang [email protected]
Cr-Commit-Position: refs/heads/main@{#1436368}