Migrate language block 46 - canonical_const ... char_escape.

tests/language_strong/cascade2_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.
-
-// Regression test for dart2js that used to hit an assertion in the
-// container tracer visitor in the presence of cascaded calls.
-
-import "package:expect/expect.dart";
-
-class A {
-  var foo;
-
-  add(list) {
-    foo = list;
-    list.add(2.5);
-    return this;
-  }
-
-  call(arg) => arg;
-}
-
-main() {
-  // Strong mode change: add explicit <dynamic>
-  var foo = <dynamic>[42, 0];
-  var a = new A();
-  var bar = a..add(foo)('WHAT');
-  a..foo[0] = new Object();
-  Expect.throws(() => foo[0] + 2, (e) => e is NoSuchMethodError);
-}