Add layout tests to check Accept request header values observed by Service Worker

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js
index 1443681f41b470e832a4898c6fdf5732ccbe3fa7..7e54b2a6943c3c0d0eab777f40e7d0ae562a2b0e 100644
--- a/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-event-test-worker.js
@@ -11,6 +11,11 @@ function handleReferrer(event) {
     ['Referrer: ' + event.request.referrer])));
 }
 
+function handleAccept(event) {
+  event.respondWith(new Response(new Blob(
+    ['Accept: ' + event.request.headers.get('accept')])));
+}
+
 function handleClientId(event) {
   var body;
   if (event.clientId !== null) {
@@ -76,6 +81,7 @@ self.addEventListener('fetch', function(event) {
       { pattern: '?string', fn: handleString },
       { pattern: '?blob', fn: handleBlob },
       { pattern: '?referrer', fn: handleReferrer },
+      { pattern: '?accept', fn: handleAccept },
       { pattern: '?clientId', fn: handleClientId },
       { pattern: '?ignore', fn: function() {} },
       { pattern: '?null', fn: handleNullBody },