Revert "Remove Registry from registerMetadataConstant" and "Serialize metadata"

pkg/compiler/lib/src/serialization/equivalence.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Functions for asserting equivalence across serialization.
 
 library dart2js.serialization.equivalence;
 
 import '../closure.dart';
 import '../common.dart';
@@ skipping 1814 matching lines @@
   @override
   bool visitStatement(Statement node1, Statement node2) {
     throw new UnsupportedError('Unexpected nodes: $node1 <> $node2');
   }
 
   @override
   bool visitStringNode(StringNode node1, StringNode node2) {
     throw new UnsupportedError('Unexpected nodes: $node1 <> $node2');
   }
 }
-
-bool areMetadataAnnotationsEquivalent(
-    MetadataAnnotation metadata1, MetadataAnnotation metadata2) {
-  if (metadata1 == metadata2) return true;
-  if (metadata1 == null || metadata2 == null) return false;
-  return areElementsEquivalent(
-          metadata1.annotatedElement, metadata2.annotatedElement) &&
-      areConstantsEquivalent(metadata1.constant, metadata2.constant);
-}