fix future onError handler wrapping to avoid cast error

sdk/lib/async/stream_impl.dart

Index: sdk/lib/async/stream_impl.dart
diff --git a/sdk/lib/async/stream_impl.dart b/sdk/lib/async/stream_impl.dart
index 29cfbd1c3ce5cc1055f0f5240734352e7be9b7d3..9cecbb0009fdb2b0f211ad2eb0d214c54c617d6c 100644
--- a/sdk/lib/async/stream_impl.dart
+++ b/sdk/lib/async/stream_impl.dart
@@ -144,9 +144,7 @@ class _BufferingStreamSubscription<T> implements StreamSubscription<T>,
 
   void onError(Function handleError) {
     if (handleError == null) handleError = _nullErrorHandler;
-    // We are not allowed to use 'void' as type argument for the generic type,
-    // so we use 'dynamic' instead.
-    _onError = _registerErrorHandler<dynamic>(handleError, _zone);
+    _onError = _registerErrorHandler(handleError, _zone);
   }
 
   void onDone(void handleDone()) {