Migrate language block 46 - canonical_const ... char_escape.

tests/language_2/canonical_const3_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.
 //
 // Check proper canonicalization (fields must be canonicalized as well).
 
 import "package:expect/expect.dart";
 
 main() {
   Expect.isFalse(identical(new Duration(days: 1), new Duration(days: 1)));
   Expect.isTrue(identical(const Duration(days: 2), const Duration(days: 2)));
   Expect.isTrue(identical(const B(3.0), const B(3.0)));
   Expect.isTrue(identical(const F(main), const F(main)));
 }
 
 class A {
   final a;
   const A(v) : a = v + 3.4;
 }
 
 class B extends A {
   final b;
   const B(v)
-      : super(v),
-        b = v + 1.0;
+      : b = v + 1.0,
+        super(v);
 }
 
 class F {
   final f;
   const F(v) : f = v;
 }