On OCE here, think Australia, which we do have some levels of anti-Chinese mentality going on for one reason or the other (not implying it's justified, because it isn't, just saying there's a couple reason why this happened), I also do occasionally run into this kind of abuse outside of the more ""typical"" (sad, isn't it?) slurs regarding Jews, Muslims and black people.
Obviously, just report them. No need to think more than that. If you are seriously disturbed by the kind of horse shit they spew and before you're out of the match to have access to the report, you can also save your brain cells by muting them; if you have to, you can also screen cap and send it raw to Riot Support via a support ticket, that's another way of reporting questionable player behaviours.
Also, after you're done with the match, wait a while before you re-queue. You don't want to run into them again.