Produces invalid css when using inherit for part of border-radius

[wotnak]

div {
  border-radius: inherit;
  border-bottom-left-radius: 0;
  border-bottom-right-radius: 0;
}

should be left as is but is transformed to

div {
  border-radius: inherit 0 0 inherit;
}

inherit can only be used as the whole value of a given property. Using it as part of a shorthand property value results in browsers regarding the entire value as invalid. Similar behavior is used for other explicit defaulting keywords (unset, initial) https://www.w3.org/TR/css-cascade-3/#defaulting-keywords.

Basically #1657 but for border-radius.