Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_strong/checked_setter2_test.dart

-// Copyright (c) 2013, 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 implicit setters in checked mode do a type check generic types.
-
-import "package:expect/expect.dart";
-
-class A {
-  C<int> c;
-}
-
-class B extends A {}
-
-class C<T> {}
-
-var array = [new B()];
-
-main() {
-  array[0].c = new C();
-  bool inCheckedMode = false;
-  try {
-    var i = 42;
-    String a = i;
-  } catch (e) {
-    inCheckedMode = true;
-  }
-  if (inCheckedMode) {
-    Expect.throws(() => array[0].c = new C<bool>(), (e) => e is TypeError);
-  }
-}