optimize self-references in generic type definitions

test/codegen/language/generic_self_reference_test.dart

 // Copyright (c) 2016, 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.
 
 import "package:expect/expect.dart";
 
+class Bar<T> {
+}
+
+class Foo<T> extends Bar<Foo<T>> {
+}
+
 void main() {
-  dynamic x = 3;
-  Expect.equals(3, x.hashCode);
+  print(new Foo<int>());
 }