Ticket #31672: 31672.2.diff

src/wp-includes/theme.php

@@ -1460 +1460 @@
                         }
                 }
         }
-        return $stylesheets;
+        /**
+         * Filter the editor stylesheets.
+         *
+         * @since 4.2.0
+         *
+         * @param array $stylesheets Array of stylesheets to be applied to the editor.
+         */
+        return apply_filters( 'editor_stylesheets', $stylesheets );
 }
 
 /**