Begin writing tests of the runtime checks needed for Dart 2.0 soundness.

pkg/front_end/testcases/runtime_checks/dynamic_invocation_generic.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.
+
+/*@testedFeatures=checks*/
+library test;
+
+class C<T> {
+  void f< /*@checkFormal=semiSafe*/ U extends T>(U x) {}
+}
+
+void g1(dynamic d) {
+  d.f<num> /*@checkCall=dynamic*/ (1.5);
+}
+
+void g2(dynamic d) {
+  d.f /*@checkCall=dynamic*/ (1.5);
+}
+
+void test() {
+  g1(new C<int>());
+  g2(new C<int>());
+}
+
+main() {}