Ignore unused classes when constructing set for deferred loading.

tests/compiler/dart2js_extra/deferred/deferred_unused_classes_test.dart

Index: tests/compiler/dart2js_extra/deferred/deferred_unused_classes_test.dart
diff --git a/tests/lib/async/intercept_run_async1_test.dart b/tests/compiler/dart2js_extra/deferred/deferred_unused_classes_test.dart
similarity index 53%
copy from tests/lib/async/intercept_run_async1_test.dart
copy to tests/compiler/dart2js_extra/deferred/deferred_unused_classes_test.dart
index c2bc9c18c5f2052d5aeff50286a0567a69d61bf0..c3e4b36c78df2650cb55558d16e300c6dcab7cfb 100644
--- a/tests/lib/async/intercept_run_async1_test.dart
+++ b/tests/compiler/dart2js_extra/deferred/deferred_unused_classes_test.dart
@@ -1,15 +1,19 @@
-// 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.
-
-import "package:expect/expect.dart";
-import 'dart:async';
-
-main() {
-  // Test that runZoned returns the result of executing the body.
-  var result = runZonedExperimental(() => 499,
-    onRunAsync: (f) {
-      Expect.fail("Unexpected invocation.");
-    });
-  Expect.equals(499, result);
-}
+// 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.
+
+// Test that deferred loader analyzer doesn't trip over unused classes.
+
+import "package:expect/expect.dart";
+import 'dart:async';
+
+@lazy import 'deferred_class_library.dart';
+
+const lazy = const DeferredLibrary('deferred_class_library');
+
+class Base {}
+
+class DerivedNotUsed extends Base {}
+
+main() {
+}