Rory McIlroy has another victory under his belt after firing a four-under-par round of 66 to win the WGC-Bridgestone Invitational at Firestone Country Club on Sunday.  McIlroy held on to beat Spain's Sergio Garcia, just as he did a few weeks ago at The Open Championship to capture his third major.  McIlroy finished at 15-under-par, two shots better than Garcia.  The victory gives McIlroy the number-one spot in the World Golf Rankings heading into next week's PGA Championship at Valhalla.  Marc Leishman finished in third place, one shot behind Garcia.  Phil Mickelson fired a season-best round of 62 on Sunday but finished tied for 15th.  Tiger Woods withdrew from the tournament after the ninth hole on Sunday with a lower-back injury.