Method get_deleter

src/butil/unique_ptr.h:327–327

    pointer operator->() const {return get();}
    pointer get() const {return ptr_.first();}
    deleter_reference       get_deleter()       {return ptr_.second();}
    deleter_const_reference get_deleter() const {return ptr_.second();}
    operator int nat::*() const {return get() ? &nat::for_bool_ : 0;}