fix future onError handler wrapping to avoid cast error

sdk/lib/async/future_impl.dart

Index: sdk/lib/async/future_impl.dart
diff --git a/sdk/lib/async/future_impl.dart b/sdk/lib/async/future_impl.dart
index eaad3b48c2e8d97ef1691845eeb8fecb26a1d3cb..eb13318ef7f797d2d4552c74b7c81aa2a1a3a014 100644
--- a/sdk/lib/async/future_impl.dart
+++ b/sdk/lib/async/future_impl.dart
@@ -237,7 +237,7 @@ class _Future<T> implements Future<T> {
     if (!identical(currentZone, _ROOT_ZONE)) {
       f = currentZone.registerUnaryCallback<FutureOr<E>, T>(f);
       if (onError != null) {
-        onError = _registerErrorHandler<T>(onError, currentZone);
+        onError = _registerErrorHandler<E>(onError, currentZone);
       }
     }
     return _thenNoZoneRegistration<E>(f, onError);