Justin, friends and a record executive had dinner in Los Angeles. During the meal, "Justin started bragging about how he has abs," a source told Us Weekly.When Rihanna joked about seeing them, the singer obliged!"Justin took off his jacket, glasses and lifted up his shirt," said an insider."Apparently he does have a little 6 pack!" Rihanna has jumped on Twitter to alert the world that she has seen Justin Bieber’s six pack! aww…Riri wrote on Twitter,
