Fix a formatting bug caused by comments in expressions.

This fixes llvm.org/PR15162.

Before:
    bool aaaaaaaaaaaaa =  // comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa || aaaaaaaaaaaaaaaaaaaaaaaaaaaa ||
                          aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ||
                          aaaaaaaaaaaaaaaaaaaaaaaaaaaaa;

After:
    bool aaaaaaaaaaaaa =  // comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa || aaaaaaaaaaaaaaaaaaaaaaaaaaaa ||
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa || aaaaaaaaaaaaaaaaaaaaaaaaaaaaa;

llvm-svn: 174508