Change other futures to also have timeout take a named parameter.

tests/lib/async/future_test.dart

Index: tests/lib/async/future_test.dart
diff --git a/tests/lib/async/future_test.dart b/tests/lib/async/future_test.dart
index 20ae1c5190c5fa7ff963e5dc0a76e7a5cb443d64..ad6830a6db17c7fa0169d361d9003c36f3ea1fb0 100644
--- a/tests/lib/async/future_test.dart
+++ b/tests/lib/async/future_test.dart
@@ -808,8 +808,8 @@ class CustomFuture<T> implements Future<T> {
   Future catchError(Function onError, {bool test(e)}) =>
       _realFuture.catchError(onError, test: test);
   Future whenComplete(action()) => _realFuture.whenComplete(action);
-  Future timeout(Duration timeLimit, [void onTimeout()]) =>
-      _realFuture.timeout(timeLimit, onTimeout);
+  Future timeout(Duration timeLimit, {void onTimeout()}) =>
+      _realFuture.timeout(timeLimit, onTimeout: onTimeout);
   Stream asStream() => _realFuture.asStream();
   String toString() => "CustomFuture@${_realFuture.hashCode}";
   int get hashCode => _realFuture.hashCode;