Tests for `void`.

pkg/compiler/lib/src/js_backend/backend_impact.dart

Index: pkg/compiler/lib/src/js_backend/backend_impact.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend_impact.dart b/pkg/compiler/lib/src/js_backend/backend_impact.dart
index 0ba422fe3922074c1afedffcad203ddd933b2e40..c44a6d640004db2287e21b985aaa6905acfbcefe 100644
--- a/pkg/compiler/lib/src/js_backend/backend_impact.dart
+++ b/pkg/compiler/lib/src/js_backend/backend_impact.dart
@@ -613,6 +613,15 @@ class BackendImpacts {
     ]);
   }
 
+  BackendImpact _objectClass;
+
+  // TODO(floitsch): this should probably be a `void` impact, and not on
+  // `Object`.
+  BackendImpact get objectClass {
+    return _objectClass ??=
+        new BackendImpact(globalClasses: [helpers.voidClass]);
+  }
+
   BackendImpact _closureClass;
 
   BackendImpact get closureClass {