Check equivalence of closed world based on kernel elements.

tests/compiler/dart2js/kernel/closed_world_test.dart

Index: tests/compiler/dart2js/kernel/closed_world_test.dart
diff --git a/tests/compiler/dart2js/kernel/closed_world_test.dart b/tests/compiler/dart2js/kernel/closed_world_test.dart
index c95cb9e269d65c47597088e77882b68be787874c..b484a527ebdd5cc1805c29fb57e69329fa5dad2d 100644
--- a/tests/compiler/dart2js/kernel/closed_world_test.dart
+++ b/tests/compiler/dart2js/kernel/closed_world_test.dart
@@ -111,8 +111,8 @@ main(List<String> args) {
         typeEquivalence: (ResolutionDartType a, ResolutionDartType b) {
       return areTypesEquivalent(unalias(a), unalias(b));
     }, elementFilter: elementFilter, verbose: arguments.verbose);
-    checkClosedWorlds(
-        compiler.resolutionWorldBuilder.closedWorldForTesting, closedWorld,
+    checkClosedWorlds(compiler.resolutionWorldBuilder.closedWorldForTesting,
+        closedWorld, areElementsEquivalent,
         verbose: arguments.verbose);
   });
 }