Index: src/wp-includes/media-template.php
===================================================================
--- src/wp-includes/media-template.php	(revision 26022)
+++ src/wp-includes/media-template.php	(working copy)
@@ -416,6 +416,12 @@
 			<img src="{{ data.model.url }}" draggable="false" />
 		</div>
 
+		/*
+		 * The filter which switch disable_captions to null.
+		 *
+		 * @since 3.6.0
+		 * @param string null Disable or enable captions.
+		 */
 		<?php if ( ! apply_filters( 'disable_captions', '' ) ) : ?>
 			<label class="setting caption">
 				<span><?php _e('Caption'); ?></span>