Index: theme.php
===================================================================
--- theme.php	(revision 29209)
+++ theme.php	(working copy)
@@ -1412,6 +1412,17 @@
  * @return array If registered, a list of editor stylesheet URLs.
  */
 function get_editor_stylesheets() {
+	/**
+	 * Filter editor stylesheets output.
+	 *
+	 * @since 4.0.0
+	 *
+	 * @param array  array()  Array of stylesheets URLs.
+	 */
+	if ( $out = apply_filters( 'editor_stylesheets', array() ) ) {
+		return $out;
+	}
+
 	$stylesheets = array();
 	// load editor_style.css if the current theme supports it
 	if ( ! empty( $GLOBALS['editor_styles'] ) && is_array( $GLOBALS['editor_styles'] ) ) {