Remove AbstractVisitor.

dart/lib/compiler/implementation/resolved_visitor.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.
 
-class ResolvedVisitor<R> extends AbstractVisitor<R> {
+class ResolvedVisitor<R> extends Visitor<R> {
   TreeElements elements;
 
   ResolvedVisitor(this.elements);
 
   R visitSend(Send node) {
     if (node.isSuperCall) {
       return visitSuperSend(node);
     } else if (node.isOperator) {
       return visitOperatorSend(node);
     } else if (node.isPropertyAccess) {
@@ skipping 35 matching lines @@
   abstract R visitDynamicSend(Send node);
   abstract R visitForeignSend(Send node);
   abstract R visitStaticSend(Send node);
 
   abstract void internalError(String reason, [Node node]);
 
   R visitNode(Node node) {
     internalError("Unhandled node", node);
   }
 }