code: function mouseOnScrollbar() {
              var clickOnScrollbar = false;
              if (ev && (ev.currentTarget.children.length > 0)) {
                var child = ev.currentTarget.children[0];
                var hasScrollbar = child.scrollHeight > child.clientHeight;
                if (hasScrollbar && child.children.length > 0) {
                  var relPosX = ev.pageX - ev.currentTarget.getBoundingClientRect().left;
                  if (relPosX > child.querySelector('md-option').offsetWidth)
                    clickOnScrollbar = true;
                }
              }
              return clickOnScrollbar;
            }
docs: check if the mouseup event was on a scrollbar