Parsing stalls on complex `font-family`

[amiller-gh]

The parser hangs when parsing font-family. Specific decl it is having trouble with in my case is:

:scope {
  font-family: -apple-system, system-ui, "BlinkMacSystemFont", "Segoe UI", "Roboto", "Helvetica Neue", "Fira Sans", "Ubuntu", "Oxygen", "Oxygen Sans", "Cantarell", "Droid Sans", "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Lucida Grande", "Helvetica", "Arial", sans-serif;
}