combobox: Stop using old styling code
combobox: Stop using old styling code

Instead of get_path_for_child() use CSS nodes.

jadahl/gtk,grubersjoe/adwaita,davidgumberg/gtk,davidgumberg/gtk,davidgumberg/gtk,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,alexlarsson/gtk,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,jigpu/gtk,jigpu/gtk,jadahl/gtk,jigpu/gtk,jadahl/gtk