Use set_url_scheme() in _custom_background_cb() to properly set the scheme for the background image when is_ssl(). Props jkudish. fixes #18005

git-svn-id: http://core.svn.wordpress.org/trunk@21629 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -1125,7 +1125,7 @@ function background_color() {
  */
 function _custom_background_cb() {
 	// $background is the saved custom image, or the default image.
-	$background = get_background_image();
+	$background = set_url_scheme( get_background_image() );
 
 	// $color is the saved custom color.
 	// A default has to be specified in style.css. It will not be printed here.