Move the optimization done to get_user_by() in [21376] higher up the stack, into map_meta_cap() and is_super_admin().

This provides nearly the same benefits without possibly receiving a stale object from get_userdata(),
which could affect authentication, and introduce side effects for plugins.

see #21120.



git-svn-id: https://develop.svn.wordpress.org/trunk@21563 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/pluggable.php

@@ -133,9 +133,6 @@ if ( !function_exists('get_user_by') ) :
  * @return bool|object False on failure, WP_User object on success
  */
 function get_user_by( $field, $value ) {
-	if ( 'id' === $field && (int) $value && get_current_user_id() === (int) $value )
-		return wp_get_current_user();
-
 	$userdata = WP_User::get_data_by( $field, $value );
 
 	if ( !$userdata )