--- a/dom/media/test/mochitest.ini
+++ b/dom/media/test/mochitest.ini
@@ -792,17 +792,16 @@ tags=msg capturestream
 [test_mediatrack_consuming_mediastream.html]
 tags=msg
 [test_mediatrack_events.html]
 skip-if = toolkit == 'gonk' && debug # bug 1065924
 [test_mediatrack_parsing_ogg.html]
 [test_mediatrack_replay_from_end.html]
 [test_metadata.html]
 [test_mixed_principals.html]
-skip-if = os == 'win' && os_version == '5.1' # Skip XP. See bug Bug 1311231
 [test_mozHasAudio.html]
 [test_multiple_mediastreamtracks.html]
 [test_networkState.html]
 [test_new_audio.html]
 [test_no_load_event.html]
 [test_paused.html]
 [test_paused_after_ended.html]
 [test_play_events.html]

--- a/dom/media/test/test_mixed_principals.html
+++ b/dom/media/test/test_mixed_principals.html
@@ -17,17 +17,16 @@ https://bugzilla.mozilla.org/show_bug.cg
 <video id="v1" preload="metadata" onended="onendedcb('v1')"></video>
 <video id="v2" preload="metadata" onended="onendedcb('v2')"></video>
 
 <pre id="test">
 <script type="text/javascript">
 SimpleTest.waitForExplicitFinish();
 
 var pushPrefs = (...p) => new Promise(r => SpecialPowers.pushPrefEnv({set: p}, r));
-var throwOutside = e => setTimeout(() => { throw e; });
 
 var v1 = document.getElementById("v1");
 var v2 = document.getElementById("v2");
 var count = 0;
 
 function onendedcb(id) {
   var c = document.createElement("canvas");
   var ctx = c.getContext("2d");
@@ -40,18 +39,20 @@ function onendedcb(id) {
     ok(true, "Threw exception in toDataURL for " + id);
   }
   if (++count == 2) {
     SimpleTest.finish();
   }
 }
 
 function testMixedPrincipals(resource) {
-  if (!resource) {
+  // In some OS(XP) can not play mp4. Add this checking for the test failure.
+  if (!resource || !v1.canPlayType(resource.type)) {
     todo(false, "No types supported");
+    SimpleTest.finish();
     return;
   }
   // Make sure the media cache size(50MB) is large enough that the data could
   // be download in MediaCache completely.
   return pushPrefs(['media.cache_size', 50*1024])
   .then(() => {
 
     // Generate a random key. The first load with that key will return
@@ -79,16 +80,15 @@ function testMixedPrincipals(resource) {
     v2.src = "http://example.org/tests/dom/media/test/dynamic_redirect.sjs?key=v2_" + key + "&res=" + resource.name;
     v2.onloadeddata = function () {
       // To limit readahead, avoid racing with playback and "catching up" mode.
       v2.play();
     }
   });
 }
 
-testMixedPrincipals({ name:"pixel_aspect_ratio.mp4", type:"video/mp4", duration:28})
-.catch(e => throwOutside(e));
+testMixedPrincipals({ name:"pixel_aspect_ratio.mp4", type:"video/mp4", duration:28});
 
 </script>
 </pre>
 
 </body>
 </html>