Fix an F-bounded quantification bug (issue 9291).

tests/language/f_bounded_quantification2_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test for F-Bounded Quantification. Regression test for issue 9291.
+
+class Entities<T extends ConceptEntity<T>> implements EntitiesApi<T> { }
+
+class ConceptEntity<T extends ConceptEntity<T>> implements EntityApi { }
+
+abstract class EntityApi<T extends EntityApi<T>> { }
+
+abstract class EntitiesApi<T extends EntityApi<T>> { }
+
+class Concept extends ConceptEntity<Concept> { }
+
+main() {
+  new ConceptEntity<Concept>();
+}