LayoutTests/http/tests/contentextensions/text-track-blocked.html

<script>
if (window.testRunner)
    testRunner.waitUntilDone();

function vttLoaded()
{
    console.log("vttLoaded");
    if (window.testRunner)
        testRunner.notifyDone();
}

function vttError()
{
    console.log("vttError");
    if (window.testRunner)
        testRunner.notifyDone();
}

function videoLoaded()
{
	console.log("video loaded");
	var video = document.getElementById("video");
	video.textTracks[0].mode = "showing";
}

</script>
The following text track should not load.<br>
<video id="video" src="/media-resources/content/test.mp4" autoplay oncanplay="videoLoaded();">
<track id="track" src="/media-resources/track/captions-webvtt/captions-fast.vtt" kind="captions" srclang="en" onload="vttLoaded();" onerror="vttError();"></track>
</video>
	
	
</video>