Unify multiple sequential_promise_test definitions.

LayoutTests/http/tests/navigatorconnect/resources/test-helpers.js

 // Helper method that waits for a {success: <boolean>, result: any} reply on
 // a port and returns a promise that resolves (if success is true) or rejects
 // the promise with the value of the result attribute.
 function reply_as_promise(t, port) {
   return new Promise(function(resolve, reject) {
       var got_reply = false;
       port.onmessage = t.step_func(function(event) {
         assert_false(got_reply);
         assert_true('success' in event.data);
         assert_true('result' in event.data);
@@ skipping 72 matching lines @@
       };
       // Should use addEventListener and check source of event, but source isn't
       // set yet, so for now just assume only one wrapped port is used at a time.
       navigator.services.onmessage = function(event) {
         channel.port2.postMessage(event.data, event.ports);
       };
       return channel.port1;
     }
   );
 }
-
-var promise_tests = Promise.resolve();
-// Helper function to run promise tests one after the other.
-// TODO(ortuno): Remove once https://github.com/w3c/testharness.js/pull/115/files
-// gets through.
-function sequential_promise_test(func, name) {
-  var test = async_test(name);
-  promise_tests = promise_tests.then(function() {
-    return test.step(func, test, test);
-  }).then(function() {
-    test.done();
-  }).catch(test.step_func(function(value) {
-    // step_func catches the error again so the error doesn't propagate.
-    throw value;
-  }));
-}