WebKit export of https://bugs.webkit.org/show_bug.cgi?id=321504 - #64179

WebKit export from bug: [block-in-inline] A fieldset on a line takes its legend's overhang twice

[block-in-inline] A fieldset on a line takes its legend's overhang twice

A legend that reaches past its fieldset's border edge is carried as an intrinsic border, which
RenderBlock::borderBefore adds to the fieldset's border. The border box height the fieldset ends up with is
measured with that border in it, so RenderBox::contentBoxHeight has nothing left and clamps at zero.

updateLayoutBoxDimensions builds the geometry for a box on a line from both of those: the content box height from
the renderer, and the border from adjustBorderForTableAndFieldset, which adds the intrinsic border again. The
margin box the line gets is then max(0, H - BP) + BP, which is BP rather than H whenever the legend overhangs, so
the fieldset takes the overhang twice and its container grows by it.

The overhang belongs to the fieldset's own content: the lines inside it start below the legend. It says nothing
about the box a line holds, whose inner layout the render tree does. So take it where the fieldset is the
formatting context root and nowhere else, which leaves logicalBorder about a table's collapsed borders. The
content box size comes from what is left of the border box, since the renderer's own answer is measured against a
border that has the overhang in it. Only the fieldset's own block axis grew, which is the container's inline axis
when the two writing modes differ in orientation.

WebKit-Bug: https://bugs.webkit.org/show_bug.cgi?id=321504
WebKit-Canonical-Link: https://commits.webkit.org/319033@main