Well it is a Webkit bug. Epiphany/Gnome Web has the same issue. All they could do is either fix whats been broken in the Gtk port of Webkit for years or to star

Well it is a Webkit bug. Epiphany/Gnome Web has the same issue. All they could do is either fix whats been broken in the Gtk port of Webkit for years or to start from scratch and use Chromium instead. Neither option is one that a small developer can easily do.