getOriginalKeys() {
    const originalKeys = [];
    for (const key in this.props.usernameToStatus) {
      if (this.props.usernameToStatus[key]) {
        originalKeys.push(key);
      }
    }
    return originalKeys;
  }
Gets the order directly from each rendered child's `index` field.
Refs are not maintained in the rendered order, and neither is
`this._renderedChildren` (surprisingly).