});
}, 'Inserting an @import rule through insertRule on a constructed stylesheet throws an exception');

promise_test(t => {
    const importUrl = "support/constructable-import.css";
    const sheet = new CSSStyleSheet();

    sheet.replaceSync(`@import url("${importUrl}");`);

    const timeAfterReplaceSync = performance.now();
    let link = document.createElement("link");
    link.rel = "stylesheet";
    link.href = importUrl;

    return new Promise(resolve => {
      link.addEventListener("error", t.un