function fromUserExtent(extent, destProjection) {
  if (!userProjection) {
    return extent;
  }
  return transformExtent(extent, userProjection, destProjection);
}
Return an extent transformed from the user projection.  If no user projection
is set, the original extent is returned.
@param {import("./extent.js").Extent} extent Input extent.
@param {ProjectionLike} destProjection The destination projection.
@return {import("./extent.js").Extent} The input extent transformed.