ScrollTextWidget
Despite a similar API between ScrollTextWidget and ScrollHtmlWiget, what
they do internally doesn't quite match.
So, while ScrollHtmlWidget's resetSCroll *does* rewind back to the top,
ScrollTextWidget's doesn't, it just updates the scrollbar itself.
So, do that on our end, *before* the (re-)init, which'll call
_renderText for us.
Fix#7318