Document the event hook in wp-cron.php. see #25229.

git-svn-id: https://develop.svn.wordpress.org/trunk@25290 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-cron.php

@@ -89,6 +89,14 @@ foreach ( $crons as $timestamp => $cronhooks ) {
 
 			wp_unschedule_event( $timestamp, $hook, $v['args'] );
 
+			/**
+			 * Fires scheduled events.
+			 *
+			 * @since 2.1.0
+			 *
+			 * @param string $hook Name of the hook that was scheduled to be fired.
+			 * @param array $v['args'] The arguments to be passed to the hook.
+			 */
  			do_action_ref_array( $hook, $v['args'] );
 
 			// If the hook ran too long and another cron process stole the lock, quit.