Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartNativeBlock.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartNativeBlock.java b/compiler/java/com/google/dart/compiler/ast/DartNativeBlock.java
index 7030feef4c1a5fc5f144a78fd680b6db139d463c..c992cd48822c2d50036f4835139e17d7e18328ad 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartNativeBlock.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartNativeBlock.java
@@ -15,17 +15,11 @@ public class DartNativeBlock extends DartBlock {
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    v.visit(this, ctx);
-    v.endVisit(this, ctx);
+  public void visitChildren(ASTVisitor<?> visitor) {
   }
 
   @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
-  }
-
-  @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitNativeBlock(this);
   }
 }