Fix a test race - synchronize test completion to media's loadstart event.

third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html

Index: third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html b/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html
index 0fded5e8603868e79d0fc9bd67ad16b5c3fc364f..522ac47277f10ba0915ae1ac3d7a2065c3115153 100644
--- a/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html
+++ b/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-audio-video.html
@@ -3,13 +3,31 @@
 <video></video>
 <script>
     window.addEventListener('load', function () {
+        var windowOpener = window.opener;
+        var isAudioLoaded = false;
+        var isVideoLoaded = false;
+        function checkTestCompletion() {
+          if (isAudioLoaded && isVideoLoaded && windowOpener) {
+            windowOpener.postMessage('done', '*');
+          }
+        }
+
         // Assigning via JavaScript after 'load' rather than direclty in the
         // markup in order to avoid the console's flaky "what line am I on?"
         // autodetection.
-        document.querySelector('audio').src = "http://127.0.0.1:8080/resources/test.mp4";
-        document.querySelector('video').src = "http://127.0.0.1:8080/resources/test.mp4";
-        if (window.opener)
-            window.opener.postMessage('done', '*');
+        var audioElement = document.querySelector('audio');
+        audioElement.src = "http://127.0.0.1:8080/resources/test.mp4";
+        audioElement.addEventListener("loadstart", function(event) {
+          isAudioLoaded = true;
+          checkTestCompletion();
+        });
+
+        var videoElement = document.querySelector('video');
+        videoElement.src = "http://127.0.0.1:8080/resources/test.mp4";
+        videoElement.addEventListener("loadstart", function(event) {
+          isVideoLoaded = true;
+          checkTestCompletion();
+        });
     });
 </script>
 </body>