Put table cell content fragments into a hieararchy of fragments that
include their table row and table row group fragments. This ensures that
things like relative positioning and transforms set on rows and row
groups properly affect cells and cell content.
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
Most tests were only being run for layout-2013, not for layout-2020.
This wasn't great since layout-2020 is now the default.
So this patch unifies the lists of included tests for both layouts.
For layout-2013 this implies adding css/css-content/, css/css-logical/
and css/css-masking/clip/.
For layout-2020 this implies adding several additional css tests, and
also tests like dom/, js/, html/, etc.