Introduces the new syntax for deferred loading

tests/language/deferred_duplicate_prefix2_test.dart

Index: tests/language/deferred_duplicate_prefix2_test.dart
diff --git a/tests/language/deferred_duplicate_prefix2_test.dart b/tests/language/deferred_duplicate_prefix2_test.dart
index 9e520a8533c5e9edb458a7df429057fab57174b6..d93c4e8e743054187a53206cc9ffff952d732ff4 100644
--- a/tests/language/deferred_duplicate_prefix2_test.dart
+++ b/tests/language/deferred_duplicate_prefix2_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";
-
-@lazy import "deferred_prefix_constraints_lib.dart" as lib;  /// 01: compile-time error
+import "deferred_prefix_constraints_lib.dart" deferred as lib;  /// 01: compile-time error
 import "deferred_prefix_constraints_lib2.dart" as lib;
 
-const lazy = const DeferredLibrary('lib');
-
 void main() {}