getDraft = function(callback) {
    var draft = gmonkeyApi.getMainWindow().getOpenDraftMessages()[0];
    if (draft) {
      callback(draft);
    } else {
      if (!hasDraft()) {
        gmonkeyApi.getMainWindow().createNewCompose();
      }
      window.setTimeout(getDraft.bind(this, callback, false), 50);
    }
  }
Returns the last created open draft. If there is no draft, a new draft is
created.