fix(conference) simplify code

Unify the 2 functions used to leave the room into a single one.

conference.js

@@ -9,6 +9,7 @@ import { ENDPOINT_TEXT_MESSAGE_NAME } from './modules/API/constants';
 import { AUDIO_ONLY_SCREEN_SHARE_NO_TRACK } from './modules/UI/UIErrors';
 import AuthHandler from './modules/UI/authentication/AuthHandler';
 import UIUtil from './modules/UI/util/UIUtil';
+import VideoLayout from './modules/UI/videolayout/VideoLayout';
 import mediaDeviceHelper from './modules/devices/mediaDeviceHelper';
 import Recorder from './modules/recorder/Recorder';
 import { createTaskQueue } from './modules/util/helpers';
@@ -1329,6 +1330,10 @@ export default {
      * Used by the Breakout Rooms feature to join a breakout room or go back to the main room.
      */
     async joinRoom(roomName) {
+        // Reset VideoLayout. It's destroyed in features/video-layout/middleware.web.js so re-initialize it.
+        VideoLayout.initLargeVideo();
+        VideoLayout.resizeVideoArea();
+
         this.roomName = roomName;
 
         const { tryCreateLocalTracks, errors } = this.createInitialLocalTracks();
@@ -2884,7 +2889,7 @@ export default {
 
         Promise.all([
             requestFeedbackPromise,
-            this.leaveRoomAndDisconnect()
+            this.leaveRoom()
         ])
         .then(values => {
             this._room = undefined;
@@ -2905,27 +2910,23 @@ export default {
     /**
      * Leaves the room.
      *
+     * @param {boolean} doDisconnect - Wether leaving the room should also terminate the connection.
      * @returns {Promise}
      */
-    leaveRoom() {
-        if (room && room.isJoined()) {
-            return room.leave();
-        }
-    },
-
-    /**
-     * Leaves the room and calls JitsiConnection.disconnect.
-     *
-     * @returns {Promise}
-     */
-    leaveRoomAndDisconnect() {
+    leaveRoom(doDisconnect = true) {
         APP.store.dispatch(conferenceWillLeave(room));
 
         if (room && room.isJoined()) {
-            return room.leave().then(disconnect, disconnect);
+            return room.leave().finally(() => {
+                if (doDisconnect) {
+                    return disconnect();
+                }
+            });
         }
 
+        if (doDisconnect) {
             return disconnect();
+        }
     },
 
     /**

react/features/breakout-rooms/actions.js

@@ -199,7 +199,7 @@ export function moveToRoom(roomId?: string) {
             dispatch(setAudioMuted(audio.muted));
             dispatch(setVideoMuted(video.muted));
         } else {
-            APP.conference.leaveRoom()
+            APP.conference.leaveRoom(false /* doDisconnect */)
                 .finally(() => APP.conference.joinRoom(_roomId));
         }
     };

react/features/video-layout/middleware.web.js

@@ -15,8 +15,6 @@ import { PARTICIPANTS_PANE_CLOSE, PARTICIPANTS_PANE_OPEN } from '../participants
 
 import './middleware.any';
 
-declare var APP: Object;
-
 /**
  * Middleware which intercepts actions and updates the legacy component
  * {@code VideoLayout} as needed. The purpose of this middleware is to redux-ify