Add SXG accept header with Service Worker tests

Bug: 887201
Change-Id: Ife32574b7014616f13b5ac3ede174c6a72c7bf4e
Reviewed-on: https://chromium-review.googlesource.com/1253921Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595789}

content/test/data/sxg/service-worker-prefetch.html

+<script>
+async function register(script, scope) {
+  const registration = await navigator.serviceWorker.register(
+      script, {scope: scope})
+  await new Promise(resolve =>
+    registration.installing.addEventListener('statechange', resolve));
+}
+async function initialize() {
+  await register('service-worker-prefetch.js', './sw-prefetch-scope/');
+  document.title = "Done";
+}
+initialize();
+</script>

content/test/data/sxg/service-worker-prefetch.js

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+self.addEventListener('fetch', (event) => {
+});

content/test/data/sxg/service-worker.html

+<script>
+async function register(script, scope) {
+  const registration = await navigator.serviceWorker.register(
+      script, {scope: scope})
+  await new Promise(resolve =>
+    registration.installing.addEventListener('statechange', resolve));
+}
+async function initialize() {
+  await register('service-worker.js?generated', './sw-scope-generated/');
+  await register('service-worker.js?navigation-preload',
+                 './sw-scope-navigation-preload/');
+  await register('service-worker.js?no-respond-with',
+                 './sw-scope-no-respond-with/');
+  document.title = "Done";
+}
+initialize();
+</script>

content/test/data/sxg/service-worker.js

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+self.addEventListener('activate', (e) => {
+  if (location.href.endsWith('?navigation-preload')) {
+    e.waitUntil(self.registration.navigationPreload.enable())
+  }
+})
+
+self.addEventListener('fetch', (event) => {
+  if (location.href.endsWith('?generated')) {
+    event.respondWith(new Response(
+      '<script>\n' +
+      'window.parent.document.title =\'' +
+      event.request.headers.get('accept') + '\';\n</script>',
+      {headers:[['content-type', 'text/html']]}));
+  } else if (location.href.endsWith('?navigation-preload')) {
+    event.respondWith(event.preloadResponse);
+  }
+});

content/test/data/sxg/sw-prefetch-scope/test.html

+<title>Done</title>

content/test/data/sxg/sw-scope-navigation-preload/test.html

+<title>Done</title>

content/test/data/sxg/sw-scope-no-respond-with/test.html

+<title>Done</title>