Use ASTVisitor as in new AST.

compiler/java/com/google/dart/compiler/ast/DartLibraryDirective.java

 // 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.
 
 package com.google.dart.compiler.ast;
 
 /**
  * Implements the #library directive.
  */
 public class DartLibraryDirective extends DartDirective {
   private DartStringLiteral name;
 
   public DartLibraryDirective(DartStringLiteral name) {
     this.name = becomeParentOf(name);
   }
 
   public DartStringLiteral getName() {
     return name;
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    if (v.visit(this, ctx)) {
-      name = becomeParentOf(v.accept(name));
-    }
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
+  public void visitChildren(ASTVisitor<?> visitor) {
     name.accept(visitor);
   }
 
   @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitLibraryDirective(this);
   }
 }