When printing, accelerated content is not rendered on the printer.
Do you have the redirected x composite window enabled or not?
I cannot reproduce in either 2.8.5 or my development build (redirected x composite window enabled).
My fault, I assumed we didn't support rendering of accelerated content while printing because of printing/compositing-layer-printing.html failing after r189908. So, I guess it's an issue with the way we generate the snapshot, or simply a bug that only happens with that test, I'll investigate further.