Revert change

src/components/structures/TimelinePanel.js

@@ -418,9 +418,9 @@ var TimelinePanel = React.createClass({
                     // 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;
                 }
             }