test: verify threadId in reports

PR-URL: #31556
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

test/report/test-report-worker.js

@@ -23,6 +23,7 @@ async function basic() {
   helper.validateContent(report);
   assert.strictEqual(report.workers.length, 1);
   helper.validateContent(report.workers[0]);
+  assert.strictEqual(report.workers[0].header.threadId, w.threadId);
 
   w.postMessage({});