ServiceWorker: Modernize postMessage tests for cleanup

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/postmessage-msgport-to-client-worker.js

 self.onmessage = function(e) {
   e.waitUntil(self.clients.matchAll().then(function(clients) {
       clients.forEach(function(client) {
           var messageChannel = new MessageChannel();
           messageChannel.port1.onmessage =
-            onMessageViaMessagePort.bind(null, client);
+            onMessageViaMessagePort.bind(null, messageChannel.port1);
           client.postMessage({port: messageChannel.port2},
                              [messageChannel.port2]);
         });
     }));
 };
 
-function onMessageViaMessagePort(client, e) {
+function onMessageViaMessagePort(port, e) {

[nhiroki, 2016/10/18 06:46:03]

I changed a communication path from "client" to "port" because, according to an
expectation on postmessage-msgport-to-client.html, this test expects that a
message is routed via MessagePort (but wasn't).

   var message = e.data;
   if ('value' in message) {
-    client.postMessage({ack: 'Acking value: ' + message.value});
+    port.postMessage({ack: 'Acking value: ' + message.value});
   } else if ('done' in message) {
-    client.postMessage({done: true});
+    port.postMessage({done: true});

[falken, 2016/10/19 01:55:24]

Not sure if this works but can it just be e.ports[0].postMessage?

[nhiroki, 2016/10/19 04:00:50]

In my understanding, 'ports' array is filled only when a port is passed as
transferable in the sender-side, so e.ports[0] should be undefined here.

[falken, 2016/10/19 04:06:27]

Acknowledged.

   }
 }