Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartNativeDirective.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartNativeDirective.java b/compiler/java/com/google/dart/compiler/ast/DartNativeDirective.java
index 96c968e9a63d62a6403cc7ab992a8220401a6417..ca5025524ecd8e9d4f956583a219bfdfb6115b63 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartNativeDirective.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartNativeDirective.java
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
@@ -20,7 +20,7 @@ public class DartNativeDirective extends DartDirective {
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
-    nativeUri.accept(visitor);
+    safelyVisitChild(nativeUri, visitor);
   }
 
   @Override