rror does not invalidate the entire descriptor
    // if there's some other valid component present.
    { src: 'local(inherit), url(foo.ttf)', valid: true },
    { src: 'local("myfont"), local(unset)', valid: true },
    { src: 'local(), url(foo.ttf)', valid: true },
    { src: 'local(12px monospace), url(foo.ttf)', valid: true },
    { src: 'local("myfont") format(opentype), url(foo.ttf)', valid: true },
    { src: 'url(not a valid url/bar.ttf), url(foo.ttf)', valid: true },
    { src: 'url(foo.ttf) forma