Method UniqueLockBase

src/bvar/utils/lock_timer.h:221–225

public:
    typedef Mutex                   mutex_type;
    explicit UniqueLockBase(mutex_type& mutex) 
        : _timer(butil::Timer::STARTED), _lock(mutex.mutex()),
          _mutex(&mutex) {
        _timer.stop();
    }

    UniqueLockBase(mutex_type& mutex, std::defer_lock_t defer_lock) 
        : _timer(), _lock(mutex.mutex(), defer_lock), _mutex(&mutex) {