Edge case cors preflight race condition (DON'T SUBMIT).

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/testserver.js

+//Lets require/import the HTTP module
+var http = require('http');
+
+//Lets define a port we want to listen to
+const PORT=8888;
+
+var finish_response = function() {};
+
+//We need a function which handles requests and send response
+function handleRequest(request, response) {
+  console.log('URL: "' + request.url + '", method: ' + request.method);
+  if (request.url == '/cors-request') {
+    if (request.method == 'OPTIONS') {
+      finish_response = function() {
+        response.setHeader('Access-Control-Allow-Origin', '*');
+        response.setHeader('Access-Control-Allow-Methods', 'GET, PUT');
+        response.end();
+      }
+    } else {
+      response.setHeader('Access-Control-Allow-Origin', '*');
+      response.end('cors');
+    }
+  } else if (request.url == '/release') {
+    finish_response();
+    finish_response = function() {};
+    response.end('Released!');
+  }
+}
+
+//Create a server
+var server = http.createServer(handleRequest);
+
+//Lets start our server
+server.listen(PORT, function(){
+    //Callback triggered when server is successfully listening. Hurray!
+    console.log("Server listening on: http://localhost:%s", PORT);
+});