Various sorting callbacks have moved to \Drupal\Component\Utility\SortArray

Several callbacks used for sorting arrays have been changed to be methods on Drupal\Component\Utility\SortArray. For example, drupal_sort_weight() has been replaced by SortArray::sortByWeightElement()

Drupal 7:

uasort($operations, 'drupal_sort_weight');

Drupal 8:

uasort($operations, ['Drupal\Component\Utility\SortArray', 'sortByWeightElement']);