Scroll the caption upon video seeking

lms/static/coffee/spec/modules/video/video_caption_spec.coffee

@@ -35,6 +35,9 @@ describe 'VideoCaption', ->
       it 'bind player resize event', ->
         expect($(@player)).toHandleWith 'resize', @caption.onWindowResize
 
+      it 'bind player seek event', ->
+        expect($(@player)).toHandleWith 'seek', @caption.onUpdatePlayTime
+
       it 'bind player updatePlayTime event', ->
         expect($(@player)).toHandleWith 'updatePlayTime', @caption.onUpdatePlayTime
 

lms/static/coffee/src/modules/video/video_caption.coffee

@@ -10,6 +10,7 @@ class @VideoCaption
     $(window).bind('resize', @onWindowResize)
     $(@player).bind('resize', @onWindowResize)
     $(@player).bind('updatePlayTime', @onUpdatePlayTime)
+    $(@player).bind('seek', @onUpdatePlayTime)
     $(@player).bind('play', @onPlay)
     @$('.hide-subtitles').click @toggle
     @$('.subtitles').mouseenter(@onMouseEnter).mouseleave(@onMouseLeave)