Add generic-methods 'golden' tests for 'reify' transformation

pkg/kernel/testcases/reify/generic_methods_overriding_contravariance_test.dart

+// Copyright (c) 2017, 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 that generic methods can be overridden using the bound of a type
+// variable as the type of the parameter in the overloaded method.
+
+library generic_methods_overriding_contravariance_test;
+
+import "test_base.dart";
+
+class X {}
+
+class Y extends X {}
+
+class Z extends Y {}
+
+class C {
+  String fun<T extends Y>(T t) => "C";
+}
+
+class E extends C {
+  String fun<T extends Y>(Y y) => "E";
+}
+
+main() {
+  Y y = new Y();
+
+  C c = new C();
+  E e = new E();
+
+  expectTrue(c.fun<Y>(y) == "C");
+  expectTrue(e.fun<Y>(y) == "E");
+}