Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartIdentifier.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartIdentifier.java b/compiler/java/com/google/dart/compiler/ast/DartIdentifier.java
index a512779a70bccc4eb82c840116605638d145cd33..b32f42a6c6c22f75b19ff715ca853101664011bd 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartIdentifier.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartIdentifier.java
@@ -64,17 +64,11 @@ public class DartIdentifier extends DartExpression implements ElementReference {
   }
 
   @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.visitIdentifier(this);
   }