Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartParenthesizedExpression.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartParenthesizedExpression.java b/compiler/java/com/google/dart/compiler/ast/DartParenthesizedExpression.java
index 51c87e274ecf8a57409bd96859a4191b99f0dc2c..2a1a157647aac4cbd2da7bd3b305a8d3fcf1ab37 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartParenthesizedExpression.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartParenthesizedExpression.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.
 
@@ -25,7 +25,7 @@ public class DartParenthesizedExpression extends DartExpression {
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
-    expression.accept(visitor);
+    safelyVisitChild(expression, visitor);
   }
 
   @Override