Merge pull request #18431 from jerrybox/master

fix: closed caption can't move when mutiple videos in one page.

common/lib/xmodule/xmodule/js/src/video/09_video_caption.js

@@ -1230,7 +1230,7 @@
             },
 
             listenForDragDrop: function() {
-                var captions = document.querySelector('.closed-captions');
+                var captions = this.captionDisplayEl['0'];
 
                 if (typeof Draggabilly === 'function') {
                     new Draggabilly(captions, {containment: true});