Facebook finally launches 'Clear History' button for real

Remember almost two years ago when Facebook promised it'd give users the ability to delete the browsing history it uses to serve personalized ads? After the most leisurely rollout of all time, it's finally here. Facebook flipped the switch and made the "Off-Facebook Activity" menu available to all on Tuesday. Users in some countries, including Ireland and South Korea, had it since last August, but now it's available to everyone.  So, what is it, exactly? First of all, you can find it in the set...