Index: wp-includes/class-wp-editor.php
===================================================================
--- wp-includes/class-wp-editor.php	(revision 35748)
+++ wp-includes/class-wp-editor.php	(working copy)
@@ -262,6 +262,10 @@
 		 * @since 2.1.0
 		 *
 		 * @param string $content Default editor content.
+		 * @param string $default_editor Default enabled editor for current user.
+		 *                               Expects 'html' or 'tinymce'. If TinyMCE is disabled 
+		 *                               this filter will always receive 'html', regardless of settings
+		 *                               passed to the editor().
 		 */
 		$content = apply_filters( 'the_editor_content', $content, $default_editor );
 
Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 35748)
+++ wp-includes/formatting.php	(working copy)
@@ -3286,6 +3286,11 @@
  * @since 4.3.0
  *
  * @param string $text The text to be formatted.
+ * @param string $default_editor The default editor for the current user. It is usually either
+ *                               'html' or 'tinymce'.
+ *
+ * @see _WP_Editors()::editor()
+ *
  * @return string The formatted text after filter is applied.
  */
 function format_for_editor( $text, $default_editor = null ) {
@@ -3299,6 +3304,7 @@
 	 * @since 4.3.0
 	 *
 	 * @param string $text The formatted text.
+	 * @param string $default_editor The default editor for the current user.
 	 */
 	return apply_filters( 'format_for_editor', $text, $default_editor );
 }