code: function createDataSourceForLatLong(item, tableStructure) {
    // Create the TableDataSource and save it to item._dataSource.
    item._dataSource = new TableDataSource(
      item.terria,
      tableStructure,
      item._tableStyle,
      item.name,
      item.polling.seconds > 0
    );
    item._dataSource.changedEvent.addEventListener(
      dataChanged.bind(null, item),
      item
    );
    // Activate a column. This needed to wait until we had a dataSource, so it can trigger the legendHelper build.
    item.activateColumnFromTableStyle();
    ensureActiveColumn(tableStructure, item._tableStyle);
    item.startPolling();
    return when(true); // We're done - nothing to wait for.
  }
docs: Creates a datasource based on tableStructure provided and adds it to item. Suitable for TableStructures that contain
  lat-lon columns.
  
  @param {TableCatalogItem} item Item that tableDataSource is created for.
  @param {TableStructure} tableStructure TableStructure to use in creating datasource.
  @return {Promise}
  @private