This is just a personal preference for indentation, but, can you format the sentence this way?

this._presence = new GnomeSession.Presence(
  Lang.bind (this, function(proxy, error) {
    if (error) {
      logError(error, 'Error while reading gnome-session presence');
      return;
    }
}));

I like to have the arguments on the same line in this case (the '(' above the other '(' gets a little confusing) and also, the 2 space identation for the arguments and more 2 spaces for the function body itself makes it easier to differentiate them