Disable Chrome minimum font-size 10px
i can only tell WHY it's not working but this might help you to go looking for a different way to solve your problem.
from chrome version 28.0.1500.11 chrome doesn't support -webkit-text-size-adjust anymore. (changelist is here: http://trac.webkit.org/changeset/145168). and safari follows along. on newer mac os versions text-size-adjust is already gone too.
I have problems with it as well, since i've built a whole website on rem units to make it not only responsive but totally flexible. this worked pretty nice but all of a sudden everything is huge now. i'm working hard on a solution for this, but if anyone has an idea i didn't think of i'd appreciate that very much.
as soon as i find a solution i'll come back to let you know.