wp-admin/includes/class-bulk-upgrader-skin.php:152Displays the header before the bulk update process.
public function bulk_header() { $this->feedback( 'skin_upgrade_start' ); }Introduced in 3.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-bulk-upgrader-skin.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.