Update test/parallel/test-whatwg-webstreams-transfer.js

test/parallel/test-whatwg-webstreams-transfer.js

@@ -465,7 +465,13 @@ const theData = 'hello';
     });
 
     // We create an interval to keep the event loop alive while
-    // we wait for the stream read to complete.
+    // we wait for the stream read to complete. The reason this is needed is because there's
+    // otherwise nothing to keep the worker thread event loop alive long enough to actually
+    // complete the read from the stream. Under the covers the ReadableStream uses an
+    // unref'd MessagePort to communicate with the main thread. Because the MessagePort
+    // is unref'd, it's existence would not keep the thread alive on its own. There was previously
+    // a bug where this MessagePort was ref'd which would block the thread and main thread
+    // from terminating at all unless the stream was consumed/closed.
     const i = setInterval(() => {}, 1000);
 
     parentPort.onmessage = tracker.calls(({ data }) => {