From CSS Text Decoration,

the decorations are propagated to all in-flow children.

From CSS Display, display: contents means

The element itself does not generate any boxes, but its children and pseudo-elements still generate boxes as normal.

Then, if a decoration is specified in an element which does not generate boxes, does the decoration propagate to the descendants which generate boxes?

display: contents does not affect inheritance, but text decorations are special because they propagate using a mechanism different than inheritance. I'm not sure if it is an element-tree thing, and thus the decoration should still propagate, or if it's a box-tree thing, and thus it shouldn't.

Example: https://jsfiddle.net/203oz4jr/

<div>Foo</div>

div {
  display: contents;
  text-decoration: underline;
}

Should Foo be underlined? It's underlined on Chrome, but not on Firefox.