code: function() {
          OpenLayers.Element.removeClass(document.body, "olDragDown");
          this.documentEvents = false;
          OpenLayers.Event.stopObserving(document, "mousemove", this._docMove);
          OpenLayers.Event.stopObserving(document, "mouseup", this._docUp);
      }
docs: Method: removeDocumentEvents
  Stops observing document events when documentDrag is true and the mouse
  cursor re-enters the map viewport while dragging.