Support metadata on patches.

pkg/compiler/lib/src/elements/elements.dart

 // Copyright (c) 2012, 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.
 
 library elements;
 
 import '../compiler.dart' show
     Compiler;
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
@@ skipping 164 matching lines @@
  * minified Dart and JavaScript code in one go.  Also, we're planning
  * on adding an incremental compilation server that should be able to
  * reuse elements between compilations.  So to keep things simple, it
  * is best if the backends avoid setting state directly in elements.
  * It is better to keep such state in a table on the side.
  */
 abstract class Element implements Entity {
   String get name;
   ElementKind get kind;
   Element get enclosingElement;
-  Link<MetadataAnnotation> get metadata;
+  Iterable<MetadataAnnotation> get metadata;
 
   /// `true` if this element is a library.
   bool get isLibrary;
 
   /// `true` if this element is a compilation unit.
   bool get isCompilationUnit;
 
   /// `true` if this element is defines the scope of prefix used by one or
   /// more import declarations.
   bool get isPrefix;
@@ skipping 1457 matching lines @@
   bool get isDeclaredByField;
 
   /// Returns `true` if this member is abstract.
   bool get isAbstract;
 
   /// If abstract, [implementation] points to the overridden concrete member,
   /// if any. Otherwise [implementation] points to the member itself.
   Member get implementation;
 }