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

pkg/kernel/testcases/reify/generic_methods_simple_as_expression_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 type parameters in generic methods can be used in as-expressions.
+
+library generic_methods_simple_as_expression_test;
+
+import "test_base.dart";
+
+T cast<T>(dynamic obj) {
+  return obj as T;
+}
+
+main() {
+  expectTrue(cast<num>(42) == 42);
+}