TripAdvisor Inc. shares jumped on news Barry Diller, a former Fox and Paramount executive, is stepping down as chairman and selling his stake in the travel website to Liberty­ Interactive. Liberty bought 4.8 million shares of TripAdvisor common stock from Diller and the Diller-von Furstenberg Family Foundation for about $300 million, making it the new majority shareholder. Diller will remain a director at Newton-based TripAdvisor. Greg Maffei, Liberty’s CEO, called TripAdvisor a strong addition to Liberty’s portfolio.