code: protected void setDefaultInfoWindowLocation(){
          int s = mOriginalPoints.size();
          if (s > 0)
              mInfoWindowLocation = mOriginalPoints.get(s/2);
          else
              mInfoWindowLocation = new GeoPoint(0.0, 0.0);
      }
docs: Internal method used to ensure that the infowindow will have a default position in all cases,
  so that the user can call showInfoWindow even if no tap occured before.
  Currently, set the position on the "middle" point of the polyline.