Would you tattle on your fellow employee?

There is a new guy at the office. He is a goof off. He comes in late, leaves early, doesn’t get the job done. He is still on probation, but the boss has already had to counsel him about arriving on time and working a full shift. Today this fella was overheard telling another employee, “all I have to do is put in another month, then they’ll have too much time invested in me to fire me.” Would you tell the boss?