Index: src/wp-includes/class-wp-customize-setting.php
===================================================================
--- src/wp-includes/class-wp-customize-setting.php	(revision 29456)
+++ src/wp-includes/class-wp-customize-setting.php	(working copy)
@@ -134,6 +134,18 @@
 				 * @param WP_Customize_Setting $this WP_Customize_Setting instance.
 				 */
 				do_action( 'customize_preview_' . $this->id, $this );
+
+				/**
+				 * Fires when the WP_Customize_Setting::preview() method is called for settings
+				 * not handled as theme_mods or options.
+				 *
+				 * The dynamic portion of the hook name, $this->type, refers to the setting type.
+				 *
+				 * @since 4.1.0
+				 *
+				 * @param WP_Customize_Setting $this WP_Customize_Setting instance.
+				 */
+				do_action( 'customize_preview_' . $this->type, $this );
 		}
 	}