Hi Zhuohua,

Thanks for the bug report, and sorry it’s taken so long for someone to look at
it (the maintainers have had a busy year).

I’ve just had a look, and indeed see `\\def\\pgfsysdriver{pgfsys-tex4ht.def}'
hardcoded at `ob-latex.el:185'. However, this is inside a `(string= "html"
extension)' check, so tex4ht seem like the right driver to use here. There is
also a TODO just before it though,

┌────
│ 	  ;; TODO: this is a very different way of generating the
│ 	  ;; frame latex document than in the pdf case.  Ideally, both
│ 	  ;; would be unified.  This would prevent bugs creeping in
│ 	  ;; such as the one fixed on Aug 16 2014 whereby :headers was
│ 	  ;; not included in the SVG/HTML case.
└────

I think a patch which implements this could also allow you to change this
hardcoded string, and would be most welcome if someone were to give it a shot.

All the best,
Timothy