Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartImportDirective.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartImportDirective.java b/compiler/java/com/google/dart/compiler/ast/DartImportDirective.java
index c5c65be8acb8da4f1baf4a1b1ff94fa572b69c1b..3b91f1d458cb7e650f87c952cdd540026fef66f9 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartImportDirective.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartImportDirective.java
@@ -26,18 +26,7 @@ public class DartImportDirective extends DartDirective {
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    if (v.visit(this, ctx)) {
-      libraryUri = becomeParentOf(v.accept(libraryUri));
-      if (prefix != null) {
-        prefix = becomeParentOf(v.accept(prefix));
-      }
-    }
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
+  public void visitChildren(ASTVisitor<?> visitor) {
     libraryUri.accept(visitor);
     if (prefix != null) {
       prefix.accept(visitor);
@@ -45,7 +34,7 @@ public class DartImportDirective extends DartDirective {
   }
 
   @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitImportDirective(this);
   }
 }