message: try to not trigger rerenders in LazyRenderList
  by not creating new arrays
diff: @@ -282,6 +282,20 @@ const RoomSubList = React.createClass({
  this.setState({scrollTop: this.refs.scroller.getScrollTop()});
  },
  + _getRenderItems: function() {
  + // try our best to not create a new array
  + // because LazyRenderList rerender when the items prop
  + // is not the same object as the previous value
  + const {list, extraTiles} = this.props;
  + if (!extraTiles || !extraTiles.length) {
  + return list;
  + }
  + if (!list || list.length) {
  + return extraTiles;
  + }
  + return list.concat(extraTiles);
  + },
  +
  render: function() {
  const len = this.props.list.length + this.props.extraTiles.length;
  const isCollapsed = this.state.hidden && !this.props.forceExpand;
  @@ -297,7 +311,6 @@ const RoomSubList = React.createClass({
  {this._getHeaderJsx(isCollapsed)}
  </div>;
  } else {
  - const items = this.props.list; //.concat(this.props.extraTiles);
  return <div ref="subList" className={subListClasses}>
  {this._getHeaderJsx(isCollapsed)}
  <IndicatorScrollbar ref="scroller" className="mx_RoomSubList_scroll" onScroll={ this._onScroll }>
  @@ -306,7 +319,7 @@ const RoomSubList = React.createClass({
  height={ this.state.scrollerHeight }
  renderItem={ this.makeRoomTile }
  itemHeight={34}
  - items={items} />
  + items={this._getRenderItems()} />
  </IndicatorScrollbar>
  </div>;
  }
  