ServiceWorker: Rewrite windowclient-navigate.html test.

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js

-var port = null;
+self.addEventListener('message', function(e) {
+  var port = e.data.port;
+  var url = e.data.url;
 
-self.onmessage = function(e) {
-  port = e.data.port;
-  port.onmessage = on_message;
-  port.postMessage('ready');
-};
-
-function on_message(e) {
-  var url = e.data;
-  var client;
-
-  self.clients.matchAll({ includeUncontrolled : true }).then(function(cs) {
-        cs.forEach(function(c) { c.frameType == 'nested' && (client = c); });
-        return client.navigate(url);
+  clients.matchAll({ includeUncontrolled : true }).then(function(client_list) {
+        for (var i = 0; i < client_list.length; i++) {
+          var client = client_list[i];
+          if (client.frameType == 'nested')
+            return client.navigate(url);
+        }
       })
-    .then(function(c) {
-        if (!c)
-          port.postMessage(c);
+    .then(function(new_client) {
+        if (new_client === null)
+          port.postMessage(new_client);
         else
-          port.postMessage(c.url);
+          port.postMessage(new_client.url);
       })
-    .catch(function(e) {
-        port.postMessage(e.name);
+    .catch(function(error) {
+        port.postMessage(error.name);
       });
-}
+});