Parse parenthesized expressions.

dart/frog/leg/tree/unparser.dart

 // Copyright (c) 2011, 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.
 
 class Unparser implements Visitor {
   StringBuffer sb;
   final bool printDebugInfo;
 
   Unparser([this.printDebugInfo = false]);
 
@@ skipping 166 matching lines @@
       add(node.endToken.value);
     }
   }
 
   visitDoWhile(DoWhile node) {
     add(node.doKeyword.value);
     sb.add(' ');
     visit(node.body);
     sb.add(' ');
     add(node.whileKeyword.value);
-    sb.add(' (');
+    sb.add(' ');
     visit(node.condition);
-    sb.add(')');
     sb.add(node.endToken.value);
   }
 
   visitWhile(While node) {
     add(node.whileKeyword.value);
-    sb.add(' (');
+    sb.add(' ');
     visit(node.condition);
-    sb.add(')');
     sb.add(' ');
     visit(node.body);
   }
+
+  visitParenthesizedExpression(ParenthesizedExpression node) {
+    add(node.getBeginToken().value);
+    visit(node.expression);
+    add(node.getEndToken().value);
+  }
 }