Hartline, 28, was released by the Miami Dolphins last month after spending his first six NFL seasons with the team.
He was scheduled to make $5.9 million this season as part of a five-year, $31 million contract he signed in 2013.
Hartline has 298 career catches for 4,243 yards and 12 touchdowns, with his best season coming in 2012 when he caught 74 passes for 1,083 yards. He had only 39 receptions for a career-low 474 yards and two touchdowns while playing in all 16 games in 2014.
- Scooby Axson