Added support for skipping redundant dart2js compilations.

tests/standalone/io/skipping_dart2js_compilations_helper.dart

Index: tests/standalone/io/skipping_dart2js_compilations_helper.dart
diff --git a/tests/compiler/dart2js_extra/generics_is_check1_test.dart b/tests/standalone/io/skipping_dart2js_compilations_helper.dart
similarity index 64%
copy from tests/compiler/dart2js_extra/generics_is_check1_test.dart
copy to tests/standalone/io/skipping_dart2js_compilations_helper.dart
index c616c7c482f1ed35cb00fa3fb8994c4d74a8e441..3ab0d707a986c694b695106b7bc9e001eac91540 100644
--- a/tests/compiler/dart2js_extra/generics_is_check1_test.dart
+++ b/tests/standalone/io/skipping_dart2js_compilations_helper.dart
@@ -2,10 +2,10 @@
 // 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.
 
-class Hest<X> {}
+#import ('dart:io');
 
 main() {
-  var x = new Hest<int>();
-  Expect.isTrue(x is Hest<int>);
-  Expect.isFalse(x is Hest<String>);
+  var outputFile = new Options().arguments[0];
+  var file = new File(outputFile);
+  file.createSync();
 }