Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartLabel.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartLabel.java b/compiler/java/com/google/dart/compiler/ast/DartLabel.java
index 33fdaedf16cae1d48dd2f49c96c6aca355e8764b..0d53d9287abcc8f5b3b40085aa5cc3ed73438b1d 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartLabel.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartLabel.java
@@ -52,22 +52,14 @@ public class DartLabel extends DartStatement implements HasSymbol {
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    if (v.visit(this, ctx)) {
-      statement = becomeParentOf(v.accept(statement));
-    }
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
+  public void visitChildren(ASTVisitor<?> visitor) {
     if (statement != null) {
       statement.accept(visitor);
     }
   }
 
   @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitLabel(this);
   }
 }