LayoutTests/intersection-observer/intersection-observer-target-gc-thread-crash.html

<!DOCTYPE html>
<html>
<body>
<div id="tails"></div>
<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
}

const NFDIV = 1024;    // divs per wave
const NWALK = 4;       // walker observers per wave
const NSLICE = 2;      // pin observers (cascades) per wave
const NWAVES = 6;      // total waves before finishing
const RIPE_MS = 400;   // delay between a wave's birth and its first cascade
const STEP_MS = 250;   // delay between a wave's cascades
const WAVE_MS = 700;   // delay between waves

const tailsBox = document.getElementById("tails");
window.__implPin = document.implementation;
const keep = [];

function makeWave()
{
    const frameless = document.implementation.createHTMLDocument("");
    const divs = new Array(NFDIV);
    for (let i = 0; i < NFDIV; ++i)
        divs[i] = frameless.body.appendChild(frameless.createElement("div"));

    for (let w = 0; w < NWALK; ++w) {
        const tail = tailsBox.appendChild(document.createElement("div"));
        keep.push(tail);
        const walker = new IntersectionObserver(() => { });
        for (let i = NFDIV - 1; i >= 0; --i)
            walker.observe(divs[i]);
        walker.observe(tail);
    }

    const sliceSize = NFDIV / NSLICE;
    const pins = [];
    for (let j = 0; j < NSLICE; ++j) {
        const pin = new IntersectionObserver(() => { });
        for (let i = j * sliceSize; i < (j + 1) * sliceSize; ++i)
            pin.observe(divs[i]);
        pins.push(pin);
    }
    return { pins, born: performance.now(), fired: 0 };
}

let waves = [makeWave()];
let wavesMade = 1;
let lastWave = performance.now();

const ballast = [];
for (let i = 0; i < 30000; ++i)
    ballast.push({ i, s: "b" + (i & 1023) });

function step()
{
    const now = performance.now();

    for (const wave of waves) {
        while (wave.fired < NSLICE && (now - wave.born) >= RIPE_MS + wave.fired * STEP_MS) {
            const pin = wave.pins[wave.fired++];
            const burst = [];
            for (let i = 0; i < 200000; ++i)
                burst.push({ x: i, y: [i] });
            const tail = tailsBox.appendChild(document.createElement("div"));
            keep.push(tail);
            pin.observe(tail);
        }
    }

    waves = waves.filter(wave => wave.fired < NSLICE);
    if (now - lastWave >= WAVE_MS && wavesMade < NWAVES) {
        lastWave = now;
        ++wavesMade;
        waves.push(makeWave());
    }

    if (!waves.length && wavesMade >= NWAVES) {
        document.body.appendChild(document.createTextNode("PASS did not crash"));
        if (window.testRunner)
            testRunner.notifyDone();
        return;
    }

    const garbage = [];
    for (let i = 0; i < 20000; ++i)
        garbage.push({ a: i, b: [i, now] });

    setTimeout(step, 50);
}
step();
</script>
</body>
</html>