[ServiceWorker] Update formatting for tests.

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

 self.onmessage = function(e) {
-    self.clients.getAll().then(function(clients) {
-        clients.forEach(function(client) {
-            var messageChannel = new MessageChannel();
-            messageChannel.port1.onmessage = onMessageViaMessagePort.bind(null, client);
-            client.postMessage({port: messageChannel.port2}, [messageChannel.port2]);
+  self.clients.getAll().then(function(clients) {
+      clients.forEach(function(client) {
+          var messageChannel = new MessageChannel();
+          messageChannel.port1.onmessage =
+            onMessageViaMessagePort.bind(null, client);
+          client.postMessage({port: messageChannel.port2},
+                             [messageChannel.port2]);
         });
     });
 };
 
 function onMessageViaMessagePort(client, e) {
-    var message = e.data;
-    if ('value' in message) {
-        client.postMessage({ack: 'Acking value: ' + message.value});
-    } else if ('done' in message) {
-        client.postMessage({done: true});
-    }
+  var message = e.data;
+  if ('value' in message) {
+    client.postMessage({ack: 'Acking value: ' + message.value});
+  } else if ('done' in message) {
+    client.postMessage({done: true});
+  }
 }