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

pkg/kernel/testcases/reify/generic_methods_overriding_type_propagation_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 that have bounds on type parameters can be
+// overridden, and that type propagation can be used in such methods.
+
+library generic_methods_overriding_type_propagation_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 F extends C {
+  String foobar(Z z) {
+    return "FZ";
+  }
+
+  String fun<T extends Y>(T t) {
+    if (t is Z) {
+      return this.foobar(t as Z);
+    }
+    return "FY";
+  }
+}
+
+main() {
+  Y y = new Y();
+  Z z = new Z();
+
+  C c = new C();
+  F f = new F();
+
+  expectTrue(c.fun<Y>(y) == "C");
+
+  expectTrue(f.fun<Y>(y) == "FY");
+  expectTrue(f.fun<Z>(z) == "FZ");
+}