MENLO PARK (AP) — Facebook is on a roll. The world’s largest online social network posted sharply higher earnings on Wednesday as revenue from mobile advertising continued to grow, and more people used it, more often.The company’s shares climbed nearly 4 percent in extended trading after the results came out, signaling that they could hit a record high when the stock market opens on Thursday. Investors who bought — and held on to — Facebook stock during the company’s initial public offering two years ago are now close to doubling their money.Facebook Inc. (FB) said Wednesday that it earned $788 million, or 30 cents per share, in the April-June period.