Remove sequential_promise_test helper, just use promise_test

LayoutTests/http/tests/fetch/resources/thorough-util.js

 var SCOPE = BASE_ORIGIN +
   '/fetch/resources/thorough-iframe.html?' + TEST_OPTIONS;
 var IFRAME_ORIGIN = BASE_ORIGIN;
 var BASE_URL = BASE_ORIGIN +
   '/serviceworker/resources/fetch-access-control.php?';
 var OTHER_BASE_URL = OTHER_ORIGIN +
   '/serviceworker/resources/fetch-access-control.php?';
 var REDIRECT_URL = BASE_ORIGIN +
   '/serviceworker/resources/redirect.php?Redirect=';
 var OTHER_REDIRECT_URL = OTHER_ORIGIN +
@@ skipping 379 matching lines @@
 
           test_target[2].forEach(function(checkFunc) {
               checkFunc.call(this, test_target[0], report_data);
             });
         }
       });
 }
 
 function executeTests(test_targets) {
   for (var i = 0; i < test_targets.length; ++i) {
-    sequential_promise_test(
+    promise_test(
       function(counter, t) {
         return executeTest(test_targets[counter]);
       }.bind(this, i),
       "executeTest-" + i);
   }
 }