Fix JS-backend when MirrorsUsed target a static field, but there is no mirrors usage.

tests/compiler/dart2js/mirror_tree_shaking_test.dart

Index: tests/compiler/dart2js/mirror_tree_shaking_test.dart
diff --git a/tests/compiler/dart2js/mirror_tree_shaking_test.dart b/tests/compiler/dart2js/mirror_tree_shaking_test.dart
index 5caab850c564ecd5afbd08f9820a08cf74e9d374..06e28d05944773543d22c4708f14c0f45d137ddd 100644
--- a/tests/compiler/dart2js/mirror_tree_shaking_test.dart
+++ b/tests/compiler/dart2js/mirror_tree_shaking_test.dart
@@ -45,8 +45,8 @@ main() {
                                    {});
   asyncTest(() => compiler.run(Uri.parse('memory:main.dart')).then((_) {
     Expect.isFalse(compiler.compilationFailed);
-    Expect.isFalse(compiler.enqueuer.resolution.hasEnqueuedEverything);
-    Expect.isFalse(compiler.enqueuer.codegen.hasEnqueuedEverything);
+    Expect.isFalse(compiler.enqueuer.resolution.hasEnqueuedReflectiveElements);
+    Expect.isFalse(compiler.enqueuer.codegen.hasEnqueuedReflectiveElements);
     Expect.isFalse(compiler.disableTypeInference);
     Expect.isFalse(compiler.backend.hasRetainedMetadata);
   }));