Index: wp-admin/includes/class-wp-posts-list-table.php
===================================================================
--- wp-admin/includes/class-wp-posts-list-table.php	(revision 26117)
+++ wp-admin/includes/class-wp-posts-list-table.php	(working copy)
@@ -491,6 +491,12 @@
 			$classes .= ' wp-locked';
 			$lock_holder = get_userdata( $lock_holder );
 		}
+		if ( $post->post_parent ) {
+		    $count = count( get_post_ancestors($post->ID) );
+		    $classes .= ' level-'. $count;
+		} else {
+		    $classes .= ' level-0';
+		}
 	?>
 		<tr id="post-<?php echo $post->ID; ?>" class="<?php echo implode( ' ', get_post_class( $classes, $post->ID ) ); ?>" valign="top">
 	<?php