Bug 1256079 - Append video element to the document. r=pehrsons

MozReview-Commit-ID: F0tGd4kk0mD

--HG--
extra : rebase_source : 843bbaa0f3f54424862645e2c0fbe139b501fb9f

dom/media/tests/mochitest/test_getUserMedia_loadedmetadata.html

@@ -18,6 +18,7 @@
    */
   runTest(function () {
     var v = document.createElement("video");
+    document.body.appendChild(v);
     v.preload = "metadata";
 
     var constraints = {video: true, audio: true};