docs: function TextLayerBuilder_bindMouse() {
        var div = this.textLayerDiv;
        div.addEventListener('mousedown', function (e) {
          var end = div.querySelector('.endOfContent');
          if (!end) {
            return;
          }
          // On non-Firefox browsers, the selection will feel better if the height
          // of the endOfContent div will be adjusted to start at mouse click
          // location -- this will avoid flickering when selections moves up.
          // However it does not work when selection started on empty space.
          var adjustTop = e.target !== div;
          adjustTop = adjustTop && window.getComputedStyle(end).
            getPropertyValue('-moz-user-select') !== 'none';
          if (adjustTop) {
            var divBounds = div.getBoundingClientRect();
            var r = Math.max(0, (e.pageY - divBounds.top) / divBounds.height);
            end.style.top = (r * 100).toFixed(2) + '%';
          }
          end.classList.add('active');
        });
        div.addEventListener('mouseup', function (e) {
          var end = div.querySelector('.endOfContent');
          if (!end) {
            return;
          }
          end.style.top = '';
          end.classList.remove('active');
        });
      }