fix(large-video): trigger update after timeout for 1-on-1 calls (#1599)

* fix(large-video): trigger update after timeout for 1-on-1 calls

Currently no video switch happens if a user joins audio and video
muted. For example, User A is in a call and User B joins with no
mic and camera. User A will keep seeing local video on large video.
The fix is to set a timeout, of a somewhat arbitrary 3 seconds, to
show User B on large video.

* SQUASH: wrap videoElement access in if

* SQUASH: split out remoteVideoActive logic

modules/UI/videolayout/VideoLayout.js

             remoteVideo = new RemoteVideo(user, VideoLayout, eventEmitter);
         this._setRemoteControlProperties(user, remoteVideo);
         this.addRemoteVideoContainer(id, remoteVideo);
+
+        const remoteVideosCount = Object.keys(remoteVideos).length;
+
+        if (remoteVideosCount === 1) {
+            window.setTimeout(() => {
+                const updatedRemoteVideosCount
+                    = Object.keys(remoteVideos).length;
+
+                if (updatedRemoteVideosCount === 1 && remoteVideos[id]) {
+                    this._maybePlaceParticipantOnLargeVideo(id);
+                }
+            }, 3000);
+        }
     },
 
     /**
         logger.info(resourceJid + " video is now active", videoElement);
 
         VideoLayout.resizeThumbnails(
-            false, false, function() {$(videoElement).show();});
+            false, false, () => {
+                if (videoElement) {
+                    $(videoElement).show();
+                }
+            });
 
-        // Update the large video to the last added video only if there's no
-        // current dominant, focused speaker or update it to
-        // the current dominant speaker.
+        this._maybePlaceParticipantOnLargeVideo(resourceJid);
+    },
+
+    /**
+     * Update the large video to the last added video only if there's no current
+     * dominant, focused speaker or update it to the current dominant speaker.
+     *
+     * @params {string} resourceJid - The id of the user to maybe display on
+     * large video.
+     * @returns {void}
+     */
+    _maybePlaceParticipantOnLargeVideo(resourceJid) {
         if ((!pinnedId &&
             !currentDominantSpeaker &&
             this.isLargeContainerTypeVisible(VIDEO_CONTAINER_TYPE)) ||