Handle implicit closure of toString.

dart/frog/leg/lib/js_helper.dart

Index: dart/frog/leg/lib/js_helper.dart
diff --git a/dart/frog/leg/lib/js_helper.dart b/dart/frog/leg/lib/js_helper.dart
index ca78471a909b3163ed3598c2f1b89b0d453dd6d8..e4964a246c15666dbee7690e4211e2d6b33aaab4 100644
--- a/dart/frog/leg/lib/js_helper.dart
+++ b/dart/frog/leg/lib/js_helper.dart
@@ -1363,3 +1363,6 @@ class Null {
     throw UnsupportedOperationException('new Null()');

[ngeoffray, 2012/03/25 18:35:32]

Unrelated, but there is a missing 'new' here, I do hope we don't compile this
method.

[ahe, 2012/03/25 19:49:53]

frog/leg/lib/js_helper.dart:1363:11: error: is not an expression
class(UnsupportedOperationException)
    throw UnsupportedOperationException('new Null()');
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   }
 }
+
+// TODO(ahe): We should be able to automatically generate these.

[Lasse Reichstein Nielsen, 2012/03/25 18:27:33]

I like "automatically generate" :)

[ngeoffray, 2012/03/25 18:35:32]

You can remove the "be able to"

[ahe, 2012/03/25 19:49:53]

Done.

[ahe, 2012/03/25 19:49:53]

Not sure I understand. Is there something wrong with my wording? Or are you
saying you like the idea?

+builtin$get$toString(receiver) => () => builtin$toString$0(receiver);