According to Ken Rosenthal of FOXSports.com, the Giants reached agreement on a minor league contract Saturday with outfielder Justin Christian. Christian, 30, posted a decent .289/.366/.435 batting line with nine homers and 22 stolen bases over 468 plate appearances between Double-A Trenton and Triple-A Scranton/Wilkes-Barre last season. The Lincoln, Nebraska native has spent his entire…