function fetch_tests_from_worker(port) {
        return tests.fetch_tests_from_worker(port);
    }
Get test results from a worker and include them in the current test.

@param {Worker|SharedWorker|ServiceWorker|MessagePort} port -
Either a worker object or a port connected to a worker which is
running tests..
@returns {Promise} - A promise that's resolved once all the remote tests are complete.