Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 28697)
+++ src/wp-includes/functions.php	(working copy)
@@ -3379,6 +3379,18 @@
 }
 
 /**
+ * Determine if the scheme of the given URL is https.
+ *
+ * @since 4.0.0
+ * 
+ * @param  string  $url The URL
+ * @return boolean      True if the given URL uses https, false if not (or if the URL is not valid).
+ */
+function is_https( $url ) {
+	return ( 'https' === parse_url( $url, PHP_URL_SCHEME ) );
+}
+
+/**
  * Whether SSL login should be forced.
  *
  * @since 2.6.0