Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php	(revision 32294)
+++ wp-includes/default-constants.php	(working copy)
@@ -68,6 +68,10 @@
 	if ( !defined('WP_DEBUG_LOG') )
 		define('WP_DEBUG_LOG', false);
 
+    // Add define('SCRIPT_DEBUG', true); to wp-config.php to use dev versions of core JS and CSS files
+    if ( !defined('SCRIPT_DEBUG') )
+        define( 'SCRIPT_DEBUG', false );
+
 	if ( !defined('WP_CACHE') )
 		define('WP_CACHE', false);