Should Error#message be enumerable?

[Mathias Bynens]

In most environments, Error#message is enumerable, e.g.

    try {
      LOLWAT; // throws a ReferenceError
    } catch(e) {
      for (var i in e) {
        console.log(i);
      }
    }

This enumerates the properties on the Error object and logs them one
by one to the console.

This behavior recently changed in v8, causing me to file this bug:
http://code.google.com/p/v8/issues/detail?id=1595 However, the
comments (starting at
http://code.google.com/p/v8/issues/detail?id=1595#c5) have confused
me.

Could anyone please clarify what the spec says on this topic?