k/connectedCallback");

    promise_test(async t => {
        const ce = document.getElementById("ce");
        let reactions = [];
        const outer_element_name = unique_element_name();
        const inner_element_name = unique_element_name();
        customElements.define(outer_element_name,
            class MockCustomElement extends HTMLElement {
              connectedCallback() { reactions.push("outer connected"); }
              disconnectedCallback() { reactions.push("outer disconnected"); }
    