Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartFunctionExpression.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartFunctionExpression.java b/compiler/java/com/google/dart/compiler/ast/DartFunctionExpression.java
index 06245acf23cf8aacc56608a816d0eec666564595..bf0817bb61d26fd40c70bb4b9f0c0ff65786c265 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartFunctionExpression.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartFunctionExpression.java
@@ -61,20 +61,12 @@ public class DartFunctionExpression extends DartExpression implements HasSymbol
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    if (v.visit(this, ctx)) {
-      function = becomeParentOf(v.accept(function));
-    }
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
+  public void visitChildren(ASTVisitor<?> visitor) {
     function.accept(visitor);
   }
 
   @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitFunctionExpression(this);
   }
 }