http: add comments in _http_incoming

PR-URL: #33035
Refs: #30625
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/_http_incoming.js

@@ -171,6 +171,9 @@ IncomingMessage.prototype._destroy = function _destroy(err, cb) {
 
   // If aborted and the underlying socket not already destroyed,
   // destroy it.
+  // We have to check if the socket is already destroyed because finished
+  // does not call the callback when this methdod is invoked from `_http_client`
+  // in `test/parallel/test-http-client-spurious-aborted.js`
   if (this.socket && !this.socket.destroyed && this.aborted) {
     this.socket.destroy(err);
     const cleanup = finished(this.socket, (e) => {
@@ -359,6 +362,9 @@ IncomingMessage.prototype._dump = function _dump() {
 };
 
 function onError(instance, cb, error) {
+  // This is to keep backward compatible behavior.
+  // An error is emitted only if there are listeners attached to
+  // the event.
   if (instance.listenerCount('error') > 0) {
     cb(error);
   } else {