chromium/src/third_party/blink/web_tests/http/tests/devtools/console/resources/worker-with-unhandled-promises.js

function runPromisesInWorker()
{
    Promise.reject(new Error("err1"))
        .then()
        .then()
        .then(); // Last is unhandled.

    var reject
    var m0 = new Promise(function(res, rej) { reject = rej; });
    var m1 = m0.then(function() {});
    var m2 = m0.then(function() {});
    var m3 = m0.then(function() {});
    var m4 = 0;
    m0.catch(function() {
        m2.catch(function() {
            m1.catch(function() {
                m4 = m3.then(function() {}); // Unhandled.
            });
        });
    });
    reject(new Error("err2"));
}

onmessage = function(event) {
    runPromisesInWorker();
    setInterval(doWork, 0);
}
var message_id = 0;
function doWork()
{
    postMessage("Message #" + message_id++);
}