message: Use the existing room object
  For some reason, we were getting the room object for every event during read
  receipt processing, even though it has been passed in as a prop already.
diff: @@ -52,6 +52,10 @@ module.exports = React.createClass({
  // ID of an event to highlight. If undefined, no event will be highlighted.
  highlightedEventId: PropTypes.string,
  + // The room these events are all in together, if any.
  + // (The notification panel won't have a room here, for example.)
  + room: PropTypes.object,
  +
  // Should we show URL Previews
  showUrlPreview: PropTypes.bool,
  @@ -615,7 +619,7 @@ module.exports = React.createClass({
  const myUserId = MatrixClientPeg.get().credentials.userId;
  // get list of read receipts, sorted most recent first
  - const room = MatrixClientPeg.get().getRoom(event.getRoomId());
  + const { room } = this.props;
  if (!room) {
  return null;
  }
  