Uber selected Dara Khosrowshahi, who leads the online travel company Expedia, to be its chief executive on Sunday, capping a contentious search process as the ride-hailing company seeks to move past a turbulent period. Khosrowshahi emerged as the leading candidate from a field of three finalists over a weekend of Uber board meetings, according to two people with knowledge of the process, who spoke on the condition of anonymity because the details were confidential.