admin_head-media-upload-popup
Action Hook: Fires when scripts enqueued for the admin header for the legacy (pre-3.5.0) media upload popup are printed.
Source: wp-admin/includes/media.php:601
update_gallery_tab()
Function: Adds the gallery tab back to the tabs array if post has image attachments.
Source: wp-admin/includes/media.php:44
admin_head_{$content_func}
Action Hook: Fires in the admin header for each specific form tab in the legacy (pre-3.5.0) media upload popup.
Source: wp-admin/includes/media.php:616