Migrate language block 46 - canonical_const ... char_escape.

tests/language_2/cha_deopt1_test.dart

 // Copyright (c) 2014, 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.
-// VMOptions=--optimization-counter-threshold=100
+// VMOptions=--optimization-counter-threshold=100 --no-background-compilation
 
 // Test lazy deoptimization at field guards with deferred loading.
 
 import "package:expect/expect.dart";
 import "cha_deopt1_lib.dart";
 import "cha_deopt1_deferred_lib.dart" deferred as d;
 
 var loaded = false;
 
 main() {
@@ skipping 24 matching lines @@
 class X {
   T fld = new T();
 
   test(T t) {
     if (t != null) {
       T tmp = t;
       fld = tmp;
     }
   }
 }