ServiceWorker: Spec alignment tweaks for Request/Response objects

LayoutTests/http/tests/serviceworker/resources/response-worker.js

Index: LayoutTests/http/tests/serviceworker/resources/response-worker.js
diff --git a/LayoutTests/http/tests/serviceworker/resources/response-worker.js b/LayoutTests/http/tests/serviceworker/resources/response-worker.js
index e80e2a932810809a631bc62a154d66aa65925f0e..1c493f67e8df01e5e543edc1b8266f2e98987c7f 100644
--- a/LayoutTests/http/tests/serviceworker/resources/response-worker.js
+++ b/LayoutTests/http/tests/serviceworker/resources/response-worker.js
@@ -19,4 +19,12 @@ test(function() {
     // Note: detailed behavioral tests for HeaderMap are in another test,
     // http/tests/serviceworker/headermap.html.
 
+    response.status = 123;
+    response.statusText = 'Sesame Street';
+    assert_equals(response.status, 123, 'Response.status should be writable');
+    assert_equals(response.statusText, 'Sesame Street', 'Response.statusText should be writable');
+
+    assert_throws({name:'TypeError'}, function() { response.statusText = 'invalid \u0100'; },
+                  'Response.statusText should throw on invalid ByteString');
+
 }, 'Response in ServiceWorkerGlobalScope');