emit timeline_resize in MatrixChat based on ResizeNotifier

as it's used in PersistentElement which could be used at various places

src/components/structures/MatrixChat.js

@@ -318,6 +318,9 @@ export default React.createClass({
         // N.B. we don't call the whole of setTheme() here as we may be
         // racing with the theme CSS download finishing from index.js
         Tinter.tint();
+
+        // For PersistentElement
+        this.state.resizeNotifier.on("middlePanelResized", this._dispatchTimelineResize);
     },
 
     componentDidMount: function() {
@@ -400,6 +403,7 @@ export default React.createClass({
         dis.unregister(this.dispatcherRef);
         window.removeEventListener("focus", this.onFocus);
         window.removeEventListener('resize', this.handleResize);
+        this.state.resizeNotifier.removeListener("middlePanelResized", this._dispatchTimelineResize);
     },
 
     componentWillUpdate: function(props, state) {
@@ -1667,6 +1671,10 @@ export default React.createClass({
         this._windowWidth = window.innerWidth;
     },
 
+    _dispatchTimelineResize() {
+        dis.dispatch({ action: 'timeline_resize' }, true);
+    },
+
     onRoomCreated: function(roomId) {
         dis.dispatch({
             action: "view_room",

src/components/structures/MessagePanel.js

@@ -21,7 +21,6 @@ import PropTypes from 'prop-types';
 import classNames from 'classnames';
 import shouldHideEvent from '../../shouldHideEvent';
 import {wantsDateSeparator} from '../../DateUtils';
-import dis from "../../dispatcher";
 import sdk from '../../index';
 
 import MatrixClientPeg from '../../MatrixClientPeg';
@@ -665,10 +664,6 @@ module.exports = React.createClass({
         }
     },
 
-    onResize: function() {
-        dis.dispatch({ action: 'timeline_resize' }, true);
-    },
-
     render: function() {
         const ScrollPanel = sdk.getComponent("structures.ScrollPanel");
         const WhoIsTypingTile = sdk.getComponent("rooms.WhoIsTypingTile");

src/components/structures/RoomView.js

@@ -865,10 +865,6 @@ module.exports = React.createClass({
         }
     },
 
-    onSearchResultsResize: function() {
-        dis.dispatch({ action: 'timeline_resize' }, true);
-    },
-
     onSearchResultsFillRequest: function(backwards) {
         if (!backwards) {
             return Promise.resolve(false);
@@ -1803,7 +1799,6 @@ module.exports = React.createClass({
                     <ScrollPanel ref="searchResultsPanel"
                         className="mx_RoomView_messagePanel mx_RoomView_searchResultsPanel"
                         onFillRequest={this.onSearchResultsFillRequest}
-                        onResize={this.onSearchResultsResize}
                     >
                         <li className={scrollheader_classes}></li>
                         { this.getSearchResultTiles() }