Serialize WarnOnUseElement

tests/compiler/dart2js/serialization/equivalence_test.dart

Index: tests/compiler/dart2js/serialization/equivalence_test.dart
diff --git a/tests/compiler/dart2js/serialization/equivalence_test.dart b/tests/compiler/dart2js/serialization/equivalence_test.dart
index 72acc470c084e9dc64560943f5e302e41bacdad3..cdb00ea4b08b36c820f473f055b26a02cc16d7ea 100644
--- a/tests/compiler/dart2js/serialization/equivalence_test.dart
+++ b/tests/compiler/dart2js/serialization/equivalence_test.dart
@@ -27,6 +27,7 @@ import 'test_helper.dart';
 
 const TEST_SOURCES = const <String, String>{
   'main.dart': '''
+import 'library.dart';
 import 'deferred_library.dart' deferred as prefix;
 
 asyncMethod() async {}
@@ -47,6 +48,9 @@ class Class1 {
 class DeferredClass {
 }
 ''',
+  'library.dart': '''
+class Type {}
+''',
 };
 
 main(List<String> arguments) {