message: Mark KeyBackupPanel as a pure component
  KeyBackupPanel depends only on its own state and its children are pure, so it
  can be pure as well. This avoids some unnecessary re-renders.
diff: @@ -21,7 +21,7 @@ import MatrixClientPeg from '../../../MatrixClientPeg';
  import { _t } from '../../../languageHandler';
  import Modal from '../../../Modal';
  -export default class KeyBackupPanel extends React.Component {
  +export default class KeyBackupPanel extends React.PureComponent {
  constructor(props) {
  super(props);
  