Mirror printer test.

dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index a72fe8d406af9b482cff9674cb71e852210b7b0d..980c52fcaccde3842ab439d94b2f322cb8913255 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -1438,13 +1438,7 @@ class JavaScriptBackend extends Backend {
       if (mustRetainMetadata) return;
       compiler.log('Retaining metadata.');
       mustRetainMetadata = true;
-      for (LibraryElement library in compiler.libraries.values) {
-        if (retainMetadataOf(library)) {
-          for (Link link = library.metadata; !link.isEmpty; link = link.tail) {
-            link.head.ensureResolved(compiler);
-          }
-        }
-      }
+      compiler.libraries.values.forEach(retainMetadataOf);
       for (Dependency dependency in metadataInstantiatedTypes) {
         registerMetadataInstantiatedType(dependency.type, dependency.user);
       }
@@ -1488,7 +1482,8 @@ class JavaScriptBackend extends Backend {
     if (mustRetainMetadata) hasRetainedMetadata = true;
     if (mustRetainMetadata && isNeededForReflection(element)) {
       for (MetadataAnnotation metadata in element.metadata) {
-        metadata.value.accept(new ConstantCopier(compiler.constantHandler));
+        metadata.ensureResolved(compiler)
+            .value.accept(new ConstantCopier(compiler.constantHandler));
       }
       return true;
     }