+ /**
+ * Ensure all media keys use array values.
+ *
+ * Normalises arrays returned by the ResourceLoaderFileModule::getStyles() method.
+ *
+ * @param array &$styles Associative array, keys are strings (media queries),
+ * values are strings or arrays
+ */
+ private function normalizeStyles( &$styles ) {
+ foreach ( $styles as $key => $val ) {
+ if ( !is_array( $val ) ) {
+ $styles[$key] = [ $val ];
+ }
+ }
+ }
+