Markup block - Gen<None> - 11 - (0:0,0)
    HtmlComment block - Gen<None> - 10 - (0:0,0)
        Markup span - Gen<Markup> - [<!--] - SpanEditHandler;Accepts:None - (0:0,0) - Symbols:3
            HtmlSymbolType.OpenAngle;[<];
            HtmlSymbolType.Bang;[!];
            HtmlSymbolType.DoubleHyphen;[--];
        Markup span - Gen<Markup> - [Foo] - SpanEditHandler;Accepts:WhiteSpace - (4:0,4) - Symbols:1
            HtmlSymbolType.Text;[Foo];
        Markup span - Gen<Markup> - [-->] - SpanEditHandler;Accepts:None - (7:0,7) - Symbols:2
            HtmlSymbolType.DoubleHyphen;[--];
            HtmlSymbolType.CloseAngle;[>];
    Markup span - Gen<Markup> - [ ] - SpanEditHandler;Accepts:None - (10:0,10) - Symbols:1
        HtmlSymbolType.WhiteSpace;[ ];
