message: Remove redundant setting of readMarkerEventId
diff: @@ -417,9 +417,10 @@ var TimelinePanel = React.createClass({
  } else if(lastEv && this.getReadMarkerPosition() === 0) {
  // we know we're stuckAtBottom, so we can advance the RM
  // immediately, to save a later render cycle
  +
  + // This call will setState with readMarkerEventId = lastEv.getId()
  this._setReadMarker(lastEv.getId(), lastEv.getTs(), true);
  updatedState.readMarkerVisible = false;
  - updatedState.readMarkerEventId = lastEv.getId();
  callback = this.props.onReadMarkerUpdated;
  }
  }
  