SAN JOSE - At Facebook’s annual developer’s conference, Chief Executive Mark Zuckerberg unveiled changes to the social networking platform, from a function to allow users to delete information Facebook has gathered on them to a new dating tool.Taking on a more somber and forceful tone than in previous years, Zuckerberg on Tuesday tried to bolster Facebook’s commitment to privacy and building community. He said users should have the ability to delete the browsing history Facebook collects, much in the way that browsers like Apple’s Safari and Google’s Chrome allow people to clear their tracking cookies.Zuckerberg’s appearance at the annual conference, called F8, caps a month during which he has tried to rebuild public trust in Facebook after a data privacy scandal. In March, Facebook revealed that Cambridge Analytica, a political marketing firm used by the Trump campaign, had improperly obtained the personal information of 87 million users. That prompted an outcry that Facebook was mishandling people’s data.Google and Apple allow users to permanently delete their browsing and search histories from its servers. Like Facebook, though, Google says its services will perform worse without the data it uses to, for instance, help users auto-complete their searches.In announcing the dating app, he said that Facebook should be in the business of bringing people together in new ways. He told a story of being stopped on the street by married couples who had met through Facebook, and said that he wanted to make a more deliberate effort to bring couples together.So many people are single, Zuckerberg said, "so clearly there’s something to do here!"The announcement sent the stock of Match Group, which owns properties such as Tinder, OkCupid, and Match.com, down 18 percent.Zuckerberg also announced a new virtual-reality headset, called Oculus Go, that debuted Tuesday. In an Oprah-style moment, he announced that all of the attendees would get a free $200 headset.Zuckerberg also thanked Jan Koum, the departing co-founder of the Facebook-owned messaging service WhatsApp, who announced his resignation on Monday after the Washington Post published a story that he was leaving the company after clashing with management over privacy, encryption and strategy."We built the largest fully encrypted communication network in the world," Zuckerberg said. "It wouldn’t have happened without him."- - -The Washington Post’s Drew Harwell contributed to this story.