code: function(current) {
          var bounds,
              constrainedBounds;
  
          bounds = this.getBounds(current);
  
          constrainedBounds = this._applyBoundaryConstraints(bounds);
  
          return constrainedBounds;
      }
docs: Returns bounds taking constraints into account
  Added to improve constrained panning
  @param {Boolean} current - Pass true for the current location; defaults to false (target location).
  @return {OpenSeadragon.Viewport} Chainable.