st mql1 = iframe.contentWindow.matchMedia(media);
    const mql2 = iframe.contentWindow.matchMedia(media);

    let calls = 0;
    const listener = () => {
        calls++;
    };

    mql1.addListener(listener);
    mql2.removeListener(listener);

    iframe.height = "50"; // 200x200 => 200x50
    await waitForChangesReported();

    assert_equals(calls, 1);
}, "removing listener from one MQL doesn't remove it from all MQLs");

promise_test(async t => {
    const mql = await createMQL(t);
    const listene