SHOULD he ever become governor of California, San Francisco Mayor Gavin Newsom (above) has a nickname already lined up: “I’d like to go by ‘The Gavinator,’ ” Newsom was overheard telling a guest at a dinner hosted in his honor by NBC Entertainment honcho Ben Silverman at Mr. Chow in Beverly Hills. (Silverman said he wanted to be the “the Gavin Newsom of NBC” when he took over his post in 2007.) Also at the dinner were Silverman’s buddy Ryan Seacrest, Chelsea Handler and Hollywood power agents Ari Emanuel and Kevin Huvane.