Serialize metadata

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

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index 68f11ff1a6c850f5e6f7c48332e52c50307320ed..1b0d551eff16e7ff944a5eab6c432698094280ca 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -2300,7 +2300,6 @@ class JavaScriptBackend extends Backend {
       reporter.log('Retaining metadata.');
 
       compiler.libraryLoader.libraries.forEach(retainMetadataOf);
-
       if (enqueuer.isResolutionQueue) {
         /// Register the constant value of [metadata] as live in resolution.
         void registerMetadataConstant(MetadataAnnotation metadata) {
@@ -2350,7 +2349,8 @@ class JavaScriptBackend extends Backend {
 
     // TODO(johnniwinther): We should have access to all recently processed
     // elements and process these instead.
-    compiler.enqueuer.resolution.processedElements.forEach(processElementMetadata);
+    compiler.enqueuer.resolution.processedElements
+        .forEach(processElementMetadata);
   }
 
   void onQueueClosed() {
@@ -3075,6 +3075,8 @@ class Dependency {
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
+
+  String toString() => '$annotatedElement:${constant.toStructuredText()}';
 }
 
 class JavaScriptImpactStrategy extends ImpactStrategy {