Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_strong/checked_setter3_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.
-
-import "package:expect/expect.dart";
-
-bool get inCheckedMode {
-  try {
-    var i = 42;
-    String a = i;
-  } catch (e) {
-    return true;
-  }
-  return false;
-}
-
-class A<T> {
-  T field;
-}
-
-class B<T> {
-  T field = 42; //# 01: static type warning
-}
-
-class C<T> {
-  T field = 42; //# 02: static type warning
-}
-
-main() {
-  var a = new A<String>();
-  var c = new C<int>();
-  var i = 42;
-  var s = 'foo';
-  if (inCheckedMode) {
-    Expect.throws(() => a.field = i, (e) => e is TypeError);
-    Expect.throws(() => new B<String>(), (e) => e is TypeError); //# 01: continued
-    Expect.throws(() => c.field = s, (e) => e is TypeError); //# 02: continued
-  } else {
-    a.field = i;
-    new B<String>(); //# 01: continued
-    c.field = s; //# 02: continued
-  }
-}