Bug 1331839 - Harden test_mediarecorder_bitrate.html. r=jwwang

MozReview-Commit-ID: BFNAhS7B7C6

--HG--
extra : rebase_source : a6934456b3511f9c3b32539e41db4804b30f9ff5

dom/media/test/test_mediarecorder_bitrate.html

@@ -29,10 +29,19 @@ function runTest(test, token, bitrate) {
   element.token = token;
 
   element.src = test.name;
-  element.test = test;
-  element.stream = element.mozCaptureStreamUntilEnded();
+  element.preload = "metadata";
+  element.onloadedmetadata = function () {
+    info("loadedmetadata");
+    const stream = element.mozCaptureStreamUntilEnded();
+    element.onloadedmetadata = null;
+    element.play();
+
+    const mediaRecorder = new MediaRecorder(stream, {videoBitsPerSecond: bitrate});
+    mediaRecorder.start();
+    is(mediaRecorder.state, 'recording', 'Media recorder should be recording');
+    is(mediaRecorder.stream, stream,
+     'Media recorder stream = element stream at the start of recording');
 
-  var mediaRecorder = new MediaRecorder(element.stream , {videoBitsPerSecond: bitrate});
     var onStopFired = false;
     var onDataAvailableFired = false;
     var encoded_size = 0;
@@ -109,19 +118,7 @@ function runTest(test, token, bitrate) {
         }
       }
     };
-
-  element.preload = "metadata";
-
-  element.onloadedmetadata = function () {
-    element.onloadedmetadata = null;
-    mediaRecorder.start();
-    is(mediaRecorder.state, 'recording',
-     'Media recorder should be recording');
-    is(mediaRecorder.stream, element.stream,
-     'Media recorder stream = element stream at the start of recording');
-
-    element.play();
-  }
+  };
 }
 
 manager.runTests(gMediaRecorderVideoTests, startTest);