Introduces the new syntax for deferred loading

tests/language/deferred_duplicate_prefix1_test.dart

Index: tests/language/deferred_duplicate_prefix1_test.dart
diff --git a/tests/language/deferred_duplicate_prefix1_test.dart b/tests/language/deferred_duplicate_prefix1_test.dart
index 2665a0922ac1eebfd0223e4afa201de777d45e35..fe6acca1b06d3fe4746c6243022207ba410d4730 100644
--- a/tests/language/deferred_duplicate_prefix1_test.dart
+++ b/tests/language/deferred_duplicate_prefix1_test.dart
@@ -2,11 +2,7 @@
 // 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.
 
-import "dart:async";
-
 import "deferred_prefix_constraints_lib2.dart" as lib;
-@lazy import "deferred_prefix_constraints_lib.dart" as lib; /// 01: compile-time error
-
-const lazy = const DeferredLibrary('lib');
+import "deferred_prefix_constraints_lib.dart" deferred as lib; /// 01: compile-time error
 
 void main() {}