This makes rowspan=0 work by storing notes on which group of rows we're
in for tables containing both rowgroups and rows, and using that to
respan cells with overlarge or zero rowspans.
This also gets rid of the largest_leftover_incoming_size business,
because now spans will always be correct and we'll never have any left
over.
Move display_list_builder.rs and webrender_helpers.rs
along with the new file to components/layout/display_list/
Remove apparently unused IdType enum.
Only variant used was OverflowClip.
See #19676
Anonymous nodes were previously creating duplicate stacking contexts,
one for each node in the anonymous node chain. This change eliminates
that for tables.
Additionally the use of stacking context ids based on node addresses is
no longer necessary since stacking contexts no longer control scrolling.
This is the first step in eliminating the dependency between node
addresses and ClipScrollNodes which causes issues like #16425.
Fix issues with the combination of position:sticky and tables
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Do some minor cleanups in display list building
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