After the first and second iteration of column sizing in the grid track sizing algorithm, the available width for each grid item should be defined. This should allow these items to properly resolve various margins. Row subgrids in particular need this information for their items that participate in baseline alignment in the block direction of the grid.
<rdar://problem/116369419>
Pull request: https://github.com/WebKit/WebKit/pull/18517
Committed 269424@main (d28a4da714e8): <https://commits.webkit.org/269424@main> Reviewed commits have been landed. Closing PR #18517 and removing active labels.