Migrate test block 113 to Dart 2.0.

tests/language_2/generic_function_bounds_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.
 
 import 'dart:math';
 import 'package:expect/expect.dart';
 
 void testInstantiateToBounds() {
   f<T extends num, U extends T>() => [T, U];
   g<T extends List<U>, U extends int>() => [T, U];
@@ skipping 58 matching lines @@
   Expect.equals(g.runtimeType.toString(), '<T, U>(T, U) -> num');
   Expect.equals(h(42, 123.0), '<T, U>(T, U) -> String');
 }
 
 main() {
   testInstantiateToBounds();
   testToString();
   testChecksBound();
   testSubtype();
 }