- Include vertical border spacing in row group offset calculation so
that they are axis-aligned with child row/cell elements. This makes it
so there isn't horizontal and vertical overflow caused by child
row/cell elements.
- Include horizontal border spacing in tr width calculations. This makes
it so tr elements don't have overflow anymore when there are multiple
columns.
- Apply vertical caption offset to row group top offset.
- Don't double-count top padding when calculating vertical offset for
tr and row groups.
This patch just adds the new root paintable and updates the tests
expectations. The next patch will move painting logic from the layout
viewport to the paint viewport.
The used width is already a content width, which doesn't include
borders. Border widths should be subtracted from the specified width
instead, since that initially specifies the total width including
borders, for consistent comparison. Also handle table box padding as an
additional fix.
