Show service worker navigation preload requests in DevTools Network tab

third_party/WebKit/LayoutTests/http/tests/inspector/service-workers/resources/navigation-preload-worker.php

+<?php
+// generate_token.py  http://127.0.0.1:8000 ServiceWorkerNavigationPreload -expire-timestamp=2000000000
+header("Origin-Trial: AsAA4dg2Rm+GSgnpyxxnpVk1Bk8CcE+qVBTDpPbIFNscyNRJOdqw1l0vkC4dtsGm1tmP4ZDAKwycQDzsc9xr7gMAAABmeyJvcmlnaW4iOiAiaHR0cDovLzEyNy4wLjAuMTo4MDAwIiwgImZlYXR1cmUiOiAiU2VydmljZVdvcmtlck5hdmlnYXRpb25QcmVsb2FkIiwgImV4cGlyeSI6IDIwMDAwMDAwMDB9");
+header('Content-Type: application/javascript');
+?>
+
+self.addEventListener('activate', event => {
+    event.waitUntil(
+      registration.navigationPreload.enable()
+        .then(_ => registration.navigationPreload.setHeaderValue('hello')));
+  });
+
+self.addEventListener('fetch', event => {
+    if (event.request.url.indexOf('EarlyReturn') != -1) {
+      return;
+    }
+    if (event.request.url.indexOf('RedirectError') != -1) {
+      event.respondWith(
+        event.preloadResponse
+          .then(_ => { return new Response('dummy'); }));
+      return;
+    }
+    if (event.preloadResponse) {
+      event.respondWith(event.preloadResponse);
+    }
+  });