Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_2/checked_setter_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.
 
 import "package:expect/expect.dart";
 
 class A {
   C c;
@@ skipping 11 matching lines @@
   try {
     var i = 42;
     String a = i;
   } catch (e) {
     inCheckedMode = true;
   }
   if (inCheckedMode) {
     Expect.throws(() => array[0].c = new B(), (e) => e is TypeError);
   }
 }