The British spirits giant Diageo , which owns Johnnie Walker, Baileys and Guinness, is considering the sale of its wine business, including brands like Rosenblum Cellars, Chalone, Blossom Hill and Sterling Vineyards here in the Bay Area. Wine accounts for just a fraction of London-based Diageo's roughly $46 billion in sales - just 4 percent according to a May 4 account in Drinks Business Review, an industry trade publication.