Support metadata on patches.

pkg/compiler/lib/src/native/enqueue.dart

Index: pkg/compiler/lib/src/native/enqueue.dart
diff --git a/pkg/compiler/lib/src/native/enqueue.dart b/pkg/compiler/lib/src/native/enqueue.dart
index 1f9b47b5d070e8b23178b0a348399a3fd4ea1bf6..3de82e038c447d186b439e17d0ddcb7fadc13b25 100644
--- a/pkg/compiler/lib/src/native/enqueue.dart
+++ b/pkg/compiler/lib/src/native/enqueue.dart
@@ -314,10 +314,8 @@ abstract class NativeEnqueuerBase implements NativeEnqueuer {
   String findJsNameFromAnnotation(Element element) {
     String name = null;
     ClassElement annotationClass = annotationJsNameClass;
-    for (Link<MetadataAnnotation> link = element.metadata;
-         !link.isEmpty;
-         link = link.tail) {
-      MetadataAnnotation annotation = link.head.ensureResolved(compiler);
+    for (MetadataAnnotation annotation in element.implementation.metadata) {
+      annotation.ensureResolved(compiler);
       ConstantValue value =
           compiler.constants.getConstantValue(annotation.constant);
       if (!value.isConstructedObject) continue;