[ServiceWorker] Add test for the rejected result of FetchEvent using XHR.

LayoutTests/http/tests/serviceworker/resources/fetch-cors-xhr-iframe.html

 <script src="test-helpers.js?pipe=sub"></script>
 <script>
 var path = base_path() + 'fetch-access-control.php';
 var host_info = get_host_info();
 
 function create_success_test_promise(url, with_credentials) {
   return new Promise(function(resolve, reject) {
       var xhr = new XMLHttpRequest();
       xhr.onload = resolve;
       xhr.onerror = function() {
@@ skipping 24 matching lines @@
 
 window.addEventListener('message', function(evt) {
     var port = evt.ports[0];
     create_success_test_promise(host_info['HTTP_ORIGIN'] + path, false)
       .then(function() {
           return create_failure_test_promise(
             host_info['HTTP_REMOTE_ORIGIN'] + path,
             false);
         })
       .then(function() {
+          return create_failure_test_promise('./dummy?reject', false);
+        })
+      .then(function() {
+          return create_failure_test_promise('./dummy?resolve-null', false);
+        })
+      .then(function() {
           return create_success_test_promise(
             './dummy?url=' +
              encodeURIComponent(host_info['HTTP_ORIGIN'] + path),
             false);
         })
       .then(function() {
           return create_failure_test_promise(
             './dummy?mode=no-cors&url=' +
             encodeURIComponent(host_info['HTTP_REMOTE_ORIGIN'] + path),
             false);
@@ skipping 21 matching lines @@
             true);
         })
       .then(function() {
           port.postMessage({results: 'finish'});
         })
       .catch(function(e) {
           port.postMessage({results: 'failure:' + e});
         });
   }, false);
 </script>