If you would need to flush DNS cache in newest OSX from Cuppertino you can use same command as before:
sudo killall -HUP mDNSResponder
But what if your DNS is resolving properly but in you browser you see wrong results? As it occurs browser may keep its own DNS cache which may sometimes go against your efforts.
To clean DNS cache in Chrome you need to navigate to:
and press "Clear host cache" button.