docs: public void enableFocusedScrolling(boolean enable) {
  
          if (enable) {
              if (m_handlerRegistration == null) {
                  m_handlerRegistration = addScrollHandler(new ScrollHandler() {
  
                      public void onScroll(ScrollEvent event) {
  
                          ensureFocusedScrolling();
                      }
                  });
              }
          } else if (m_handlerRegistration != null) {
              m_handlerRegistration.removeHandler();
              m_handlerRegistration = null;
          }
      }