ServiceWorker: support Response.{status,statusText,headers} [blink] (2/3)

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

+importScripts('worker-test-helpers.js');
+
+test(function() {
+    var headers = new HeaderMap;
+    headers.set('Content-Language', 'ja');
+    headers.set('Content-Type', 'text/html; charset=UTF-8');
+    headers.set('X-ServiceWorker-Test', 'response test field');
+
+    var response = new Response({
+        status: 303,
+        statusText: 'See Other',
+        headers: headers
+    });
+
+    assert_equals(response.status, 303, 'Response.status should match');
+    assert_equals(response.statusText, 'See Other', 'Response.statusText should match');
+    assert_true(response.headers instanceof HeaderMap, 'Response.headers should be HeaderMap');
+    assert_equals(response.headers.size, 3, 'Response.headers.size should match');
+    // Note: detailed behavioral tests for HeaderMap are in another test,
+    // http/tests/serviceworker/headermap.html.
+
+}, 'Response in ServiceWorkerGlobalScope');