Simplifies logic and renames a method.

Fixes tests.

modules/statistics/SpeakerStats.js

         this._userId = userId;
         this.setDisplayName(displayName);
         this._isLocalStats = isLocalStats || false;
-        this.setIsDominantSpeaker(false);
+        this.setDominantSpeaker(false);
         this.totalDominantSpeakerTime = 0;
-        this._dominantSpeakerStart = null;
+        this._dominantSpeakerStart = 0;
         this._hasLeft = false;
     }
 
      * @returns {boolean}
      */
     isDominantSpeaker() {
-        return this._isDominantSpeaker;
+        return this._dominantSpeakerStart > 0;
     }
 
     /**
      * and will record any time accumulated since starting as dominant speaker.
      * @returns {void}
      */
-    setIsDominantSpeaker(isNowDominantSpeaker) {
-        if (!this._isDominantSpeaker && isNowDominantSpeaker) {
+    setDominantSpeaker(isNowDominantSpeaker) {
+        if (!this.isDominantSpeaker() && isNowDominantSpeaker) {
             this._dominantSpeakerStart = Date.now();
-        } else if (this._isDominantSpeaker && !isNowDominantSpeaker) {
+        } else if (this.isDominantSpeaker() && !isNowDominantSpeaker) {
             const now = Date.now();
-            const timeElapsed = now - (this._dominantSpeakerStart || 0);
+            const timeElapsed = now - this._dominantSpeakerStart;
 
             this.totalDominantSpeakerTime += timeElapsed;
-            this._dominantSpeakerStart = null;
+            this._dominantSpeakerStart = 0;
         }
-
-        this._isDominantSpeaker = isNowDominantSpeaker;
     }
 
     /**
     getTotalDominantSpeakerTime() {
         let total = this.totalDominantSpeakerTime;
 
-        if (this._isDominantSpeaker) {
+        if (this.isDominantSpeaker()) {
             total += Date.now() - this._dominantSpeakerStart;
         }
 
      */
     markAsHasLeft() {
         this._hasLeft = true;
-        this.setIsDominantSpeaker(false);
+        this.setDominantSpeaker(false);
     }
 }
 

modules/statistics/SpeakerStats.spec.js

         });
 
         it('removes the user as a dominant speaker', () => {
-            speakerStats.setIsDominantSpeaker(true);
+            speakerStats.setDominantSpeaker(true);
             speakerStats.markAsHasLeft();
             expect(speakerStats.isDominantSpeaker()).toBe(false);
         });
             const domaintSpeakerTime = 100;
 
             for (let i = 0; i < domaintSpeakerEvents; i++) {
-                speakerStats.setIsDominantSpeaker(true);
+                speakerStats.setDominantSpeaker(true);
                 jasmine.clock().tick(domaintSpeakerTime);
-                speakerStats.setIsDominantSpeaker(false);
+                speakerStats.setDominantSpeaker(false);
             }
 
             expect(speakerStats.getTotalDominantSpeakerTime())

modules/statistics/SpeakerStatsCollector.js

         conference.addEventListener(
             JitsiConferenceEvents.DISPLAY_NAME_CHANGED,
             this._onDisplayNameChange.bind(this));
-        conference.xmpp.addListener(
-            XMPPEvents.SPEAKER_STATS_RECEIVED,
-            this._updateStats.bind(this));
+        if (conference.xmpp) {
+            conference.xmpp.addListener(
+                XMPPEvents.SPEAKER_STATS_RECEIVED,
+                this._updateStats.bind(this));
+        }
     }
 
     /**
             = this.stats.users[this.stats.dominantSpeakerId];
         const newDominantSpeaker = this.stats.users[dominantSpeakerId];
 
-        oldDominantSpeaker && oldDominantSpeaker.setIsDominantSpeaker(false);
-        newDominantSpeaker && newDominantSpeaker.setIsDominantSpeaker(true);
+        oldDominantSpeaker && oldDominantSpeaker.setDominantSpeaker(false);
+        newDominantSpeaker && newDominantSpeaker.setDominantSpeaker(true);
         this.stats.dominantSpeakerId = dominantSpeakerId;
     }
 

modules/xmpp/xmpp.js

 
         msg.c('speakerstats', {
             xmlns: 'http://jitsi.org/jitmeet',
-            room: `${roomJid}` })
+            room: roomJid })
             .up();
 
         this.connection.send(msg);