Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_2/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.
+
+class A<T> {
+  T field;
+}
+
+class B<T> {
+  T field = 42; //# 01: compile-time error
+}
+
+class C<T> {
+  T field = 42; //# 02: compile-time error
+}
+
+main() {
+  var a = new A<String>();
+  var c = new C<int>();
+  var i = 42;
+  var s = 'foo';
+  a.field = i; //# 03: compile-time error
+}