--- a/dom/media/test/manifest.js
+++ b/dom/media/test/manifest.js
@@ -1464,22 +1464,22 @@ function checkMetadata(msg, e, test) {
 function getPlayableVideo(candidates) {
   var resources = getPlayableVideos(candidates);
   if (resources.length > 0)
     return resources[0];
   return null;
 }
 
 function getPlayableVideos(candidates) {
-  var v = document.createElement("video");
+  var v = manifestVideo();
   return candidates.filter(function(x){return /^video/.test(x.type) && v.canPlayType(x.type);});
 }
 
 function getPlayableAudio(candidates) {
-  var v = document.createElement("audio");
+  var v = manifestVideo();
   var resources = candidates.filter(function(x){return /^audio/.test(x.type) && v.canPlayType(x.type);});
   if (resources.length > 0)
     return resources[0];
   return null;
 }
 
 // Returns the type of element that should be created for the given mimetype.
 function getMajorMimeType(mimetype) {