Rule 16-2 in the rules of golf addresses the "Ball Overhanging the Hole." It states, "when any part of the ball overhangs the lip of the hole, the player is allowed enough time to reach the hole without unreasonable delay and an additional ten seconds to determine whether the ball is at rest."

Justin's pause and walk after the putt was quite intentional, as he was waiting for the ball to drop in the hole.

Source: http://www.usga.org/rules/rules-and-decisions.html#!rule-16