Provide functionality for CSS properties that heavily use functions, such as content and font-variant-alternates, as well as ones which singly support the ability to hold multiple values (currently done through VisualStylePropertyCombiner and separate editors). Related: <https://bugs.webkit.org/show_bug.cgi?id=148720>
<rdar://problem/24407373>
The Visual styles sidebar was removed in r236298 <https://webkit.org/b/189807>.