Spacing with Font Roboto

[Karl Berry]

    LuaTeX tries to work around viewer bugs by forcing upem to 1000 and
    fixing the differences by changing the font size and adding kerning.

Inserting kerns(?!) to work around bugs in (presumably only some)
viewers does not seem like a good tradeoff? What happens when those bugs
disappear or change in future versions? TeX output is supposed to be
stable, within reason. Oh well.

    using the original TTF fonts instead of converting them to OTF

Agreed that using original fonts sounds better in general.

I don't know why Bob changed the setup, but I doubt he did it
lightly. Perhaps he can advise. -k