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+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1756118
+-->
+<head>
+ <meta charset="utf-8">
+ <title>Test for Bug 1756118: A removed ResizeObserver shouldn't keep the refresh driver ticking</title>
+ <script src="/tests/SimpleTest/SimpleTest.js"></script>
+ <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body onload="run()">
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1756118">Mozilla Bug 1756118</a>
+<div id="display">
+ <div id="resizeMe"></div>
+</div>
+<pre id="test">
+<script>
+"use strict";
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("need to allow time to pass so that we can " +
+ "detect unwanted extra refresh driver ticks");
+const gUtils = SpecialPowers.getDOMWindowUtils(window);
+
+async function addAndRemoveResizeObserver(shouldResizeTarget) {
+ // Register a resize observer:
+ let ro = new ResizeObserver(function() { info("ResizeObserver callback"); });
+ ro.observe(resizeMe);
+
+ // double-rAF to flush pending paints:
+ await new Promise(r => requestAnimationFrame(r));
+ await new Promise(r => requestAnimationFrame(r));
+
+ ok(gUtils.refreshDriverHasPendingTick,
+ "Expecting refresh driver to be ticking, with ResizeObserver registered");
+
+ // Unregister resize observer:
+ ro.unobserve(resizeMe);
+
+ // double-rAF to flush pending paints:
+ await new Promise(r => requestAnimationFrame(r));
+ await new Promise(r => requestAnimationFrame(r));
+
+ // ...and importantly: make one additional change to the document.
+ // This causes a refresh driver tick, which in buggy builds causes
+ // the refresh driver to keep ticking indefinitely. (In buggy builds, this
+ // bonus tick notifies our ResizeObserverController, and it never unregisters
+ // and hence keeps the refresh driver ticking from that point on.)
+ resizeMe.style.height = "100px";
+}
+
+async function expectTicksToStop() {
+ let didStopTicking = false;
+ // Note: The maximum loop count here is an arbitrary large value, just to let
+ // us gracefully handle edge cases where multiple setTimeouts resolve before
+ // a pending refresh driver tick. Really, we just want to be sure the refresh
+ // driver *eventually* stops ticking, and we can do so gracefully by polling
+ // with some generous-but-finite number of checks here.
+ for (var i = 0; i < 100; i++) {
+ await new Promise(r => setTimeout(r, 8));
+ if(!gUtils.refreshDriverHasPendingTick) {
+ didStopTicking = true;
+ break;
+ }
+ }
+ ok(didStopTicking, "refresh driver should have eventually stopped ticking");
+}
+
+async function run() {
+ // By default, the refresh driver ticks on its own for some period of time
+ // after pageload. Turn that off so we don't have to wait it out:
+ await SpecialPowers.pushPrefEnv({'set':
+ [['layout.keep_ticking_after_load_ms', 0]]});
+
+ // Start out with a double-rAF, to flush paints from pageload:
+ await new Promise(r => requestAnimationFrame(r));
+ await new Promise(r => requestAnimationFrame(r));
+
+ await addAndRemoveResizeObserver(true);
+ await expectTicksToStop();
+
+ SimpleTest.finish();
+}
+</script>
+</pre>
+</body>
+</html>