Implement redirect() API for Fetch Response

LayoutTests/http/tests/fetch/script-tests/headers-guard.js

Index: LayoutTests/http/tests/fetch/script-tests/headers-guard.js
diff --git a/LayoutTests/http/tests/fetch/script-tests/headers-guard.js b/LayoutTests/http/tests/fetch/script-tests/headers-guard.js
index 00ce90bed40ecc69756ccfb6ec9a639c55736d9b..8cee05417a0810be970a24ef5decca96e5f4bd10 100644
--- a/LayoutTests/http/tests/fetch/script-tests/headers-guard.js
+++ b/LayoutTests/http/tests/fetch/script-tests/headers-guard.js
@@ -368,7 +368,10 @@ promise_test(function(t) {
         [res.headers,
          res.clone().headers,
          Response.error().headers,
-         Response.error().clone().headers].forEach(function(headers) {
+         Response.error().clone().headers,
+         Response.redirect('https://www.example.com/test.html').headers,
+         Response.redirect('https://www.example.com/test.html').clone().headers
+        ].forEach(function(headers) {
             testInvalidNamesAndValues(headers);
 
             // Test that TypeError is thrown for all header names.