Use ASTVisitor as in new AST.

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

Index: compiler/java/com/google/dart/compiler/ast/DartSourceDirective.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartSourceDirective.java b/compiler/java/com/google/dart/compiler/ast/DartSourceDirective.java
index a33c40930fe3ee2e966af1c8b47741e0f41f1a74..a9432330ea26b99215da49e2734b1d540b90de1c 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartSourceDirective.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartSourceDirective.java
@@ -19,20 +19,12 @@ public class DartSourceDirective extends DartDirective {
   }
 
   @Override
-  public void traverse(DartVisitor v, DartContext ctx) {
-    if (v.visit(this, ctx)) {
-      sourceUri = becomeParentOf(v.accept(sourceUri));
-    }
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public void visitChildren(DartPlainVisitor<?> visitor) {
+  public void visitChildren(ASTVisitor<?> visitor) {
     sourceUri.accept(visitor);
   }
 
   @Override
-  public <R> R accept(DartPlainVisitor<R> visitor) {
+  public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitSourceDirective(this);
   }
 }