ToT now enables USE=ipv6 by default. we were manually setting USE=ipv6 on a number of packages as we noticed "hey we want IPv6 in xxx", so this flips the settings for all the rest. except curl because there's a known issue there.
if anyone notices weird network behavior, prob want to look at this first :).
this shouldn't have any real user facing change in behavior though as Chrome itself has always supported IPv6.
-mike