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Test Info:

<title>Test loading of the same resource in multiple elements</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
<script type="text/javascript" src="manifest.js"></script>
<pre id="test">
<script class="testbody" type="text/javascript">
var manager = new MediaTestManager;
function checkDuration(actual, expected, name) {
ok(Math.abs(actual - expected) < 0.1,
`${name} duration: ${actual} expected: ${expected}`);
function cloneLoaded(event) {
var e =;
ok(true, `${e.token} loaded OK`);
checkDuration(e.duration, e._expectedDuration, e.token);
function tryClone(e) {
var clone = e.cloneNode(false);
clone.token = `${e.token}(cloned)`;
// Log events for debugging.
var events = ["suspend", "play", "canplay", "canplaythrough", "loadstart", "loadedmetadata",
"loadeddata", "playing", "ended", "error", "stalled", "emptied", "abort",
"waiting", "pause"];
function logEvent(evt) {
var event =;
info(`${event.token} got ${evt.type}`);
events.forEach(function(event) {
clone.addEventListener(event, logEvent);
checkDuration(e.duration, e._expectedDuration, e.token);
clone._expectedDuration = e._expectedDuration;
clone.addEventListener("loadeddata", cloneLoaded, {once: true});
clone.addEventListener("loadstart", function(evt) {
info(`${} starts loading.`);
// Since there is only one H264 decoder instance, we have to delete the
// decoder of the original element for the cloned element to load. However,
// we can't delete the decoder too early otherwise cloning decoder will
// fail to kick in. We wait for 'loadstart' event of the cloned element to
// know when the decoder is already cloned and we can delete the decoder of
// the original element.
}, {once: true});
// This test checks that loading the same URI twice in different elements at the same time
// uses the same resource without doing another network fetch. One of the gCloneTests
// uses dynamic_resource.sjs to return one resource on the first fetch and a different resource
// on the second fetch. These resources have different lengths, so if the cloned element
// does a network fetch it will get a resource with the wrong length and we get a test
// failure.
async function initTest(test, token) {
var e = document.createElement("video");
e.preload = "auto";
e.src =;
e._expectedDuration = test.duration;
ok(true, `Trying to load ${}, duration=${test.duration}`);
e.token = token;
// Since 320x240.ogv is less than 32KB, we need to wait for the
// 'suspend' event to ensure the partial block is flushed to the cache
// otherwise the cloned resource will create a new channel when it
// has no data to read at position 0. The new channel will download
// a different file than the original resource and fail the duration
// test.
let p1 = once(e, "loadeddata");
let p2 = once(e, "suspend");
await p1;
await p2;
{"set": [
["logging.MediaDecoder", "Debug"],
["logging.HTMLMediaElement", "Debug"],
["logging.MediaCache", "Debug"],
manager.runTests.bind(manager, gCloneTests, initTest));