Test that @font-feature-values sub-rules can be edited
==== Style sheet text ====

  div {
    font-family: Bixa;
    font-variant-alternates: swash(fancy);
  }

  @font-feature-values Bixa {
    @stylistic {
      donttouch: 8;
    }
    @swash {
      fancy: 2;
      boring: 1;
    }
    @styleset {
      preserve: 9;
    }
  }