Add a visitor for Elements

sdk/lib/_internal/compiler/implementation/scanner/class_element_parser.dart

 // Copyright (c) 2011, 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.
 
 part of scanner;
 
 class ClassElementParser extends PartialParser {
   ClassElementParser(Listener listener) : super(listener);
 
   Token parseClassBody(Token token) => fullParseClassBody(token);
@@ skipping 43 matching lines @@
       });
     });
     return cachedNode;
   }
 
   Token position() => beginToken;
 
   // TODO(johnniwinther): Ensure that modifiers are always available.
   Modifiers get modifiers =>
       cachedNode != null ? cachedNode.modifiers : Modifiers.EMPTY;
+
+  accept(ElementVisitor visitor) => visitor.visitPartialClassElement(this);
 }
 
 class MemberListener extends NodeListener {
   final ClassElement enclosingElement;
 
   MemberListener(DiagnosticListener listener,
                  Element enclosingElement)
       : this.enclosingElement = enclosingElement,
         super(listener, enclosingElement.getCompilationUnit());
 
@@ skipping 117 matching lines @@
 
   void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
     popNode(); // Discard arguments.
     if (periodBeforeName != null) {
       popNode(); // Discard name.
     }
     popNode(); // Discard node (Send or Identifier).
     pushMetadata(new PartialMetadataAnnotation(beginToken, endToken));
   }
 }