The San Francisco Board of Supervisors on Tuesday passed legislation requiring that undocumented youth be turned over to federal immigration officials for possible deportation only after they're convicted of a felony - not upon their arrest. The 8-2 vote, enough to override an expected veto from Mayor Gavin Newsom, prompted loud cheers from scores of immigrant rights advocates, clergy and high school students who packed the board meeting - but the jubilation may not last long.