Investors pulled a record $3.5 billion in December from Jeffrey Gundlach’s DoubleLine Total Return Bond Fund, according to Bloomberg estimates, and its annual performance trailed the benchmark index for the first time. The $55.7 billion fund, which invests predominately in mortgage-backed securities, returned 2.2 percent in 2016, compared with 2.7 percent for the Bloomberg Barclays U.S. Aggregate index.