Add second argument to Future error handlers.

sdk/lib/_internal/pub/lib/src/error_group.dart

Index: sdk/lib/_internal/pub/lib/src/error_group.dart
diff --git a/sdk/lib/_internal/pub/lib/src/error_group.dart b/sdk/lib/_internal/pub/lib/src/error_group.dart
index 1130ef97e941a69fd3ab6056668a61b0129cc82e..8d73f84f00b28a69a314b9033af29ac29230b678 100644
--- a/sdk/lib/_internal/pub/lib/src/error_group.dart
+++ b/sdk/lib/_internal/pub/lib/src/error_group.dart
@@ -179,12 +179,12 @@ class _ErrorGroupFuture implements Future {
     _completer.future.catchError((_) {});
   }
 
-  Future then(onValue(value), {onError(error)}) {
+  Future then(onValue(value), { Function onError }) {
     _hasListeners = true;
     return _completer.future.then(onValue, onError: onError);
   }
 
-  Future catchError(onError(error), {bool test(Object error)}) {
+  Future catchError(Function onError, {bool test(Object error)}) {
     _hasListeners = true;
     return _completer.future.catchError(onError, test: test);
   }