feat(PerformanceObserverStats) remove it (#2809)

It hasn't been useful or used in years.

Author: saghul

JitsiConference.js

@@ -484,11 +484,6 @@ JitsiConference.prototype._init = function(options = {}) {
         Statistics.analytics.addPermanentProperties({
             'callstats_name': this._statsCurrentId
         });
-
-        // Start performance observer for monitoring long tasks
-        if (config.longTasksStatsInterval) {
-            this.statistics.attachLongTasksStats();
-        }
     }
 
     this.eventManager.setupChatRoomListeners();

modules/statistics/PerformanceObserverStats.js

@@ -1,4 +1,3 @@
-import * as JitsiConferenceEvents from '../../JitsiConferenceEvents';
 import { JitsiTrackEvents } from '../../JitsiTrackEvents';
 import { FEEDBACK } from '../../service/statistics/AnalyticsEvents';
 import * as StatisticsEvents from '../../service/statistics/Events';
@@ -9,7 +8,6 @@ import WatchRTC from '../watchRTC/WatchRTC';
 
 import analytics from './AnalyticsAdapter';
 import LocalStats from './LocalStatsCollector';
-import { PerformanceObserverStats } from './PerformanceObserverStats';
 import RTPStats from './RTPStatsCollector';
 
 const logger = require('@jitsi/logger').getLogger('modules/statistics/statistics');
@@ -34,10 +32,6 @@ Statistics.init = function(options) {
         Statistics.audioLevelsInterval = options.audioLevelsInterval;
     }
 
-    if (typeof options.longTasksStatsInterval === 'number') {
-        Statistics.longTasksStatsInterval = options.longTasksStatsInterval;
-    }
-
     Statistics.disableThirdPartyRequests = options.disableThirdPartyRequests;
 
     LocalStats.init();
@@ -229,31 +223,6 @@ Statistics.prototype.addLongTasksStatsListener = function(listener) {
     this.eventEmitter.on(StatisticsEvents.LONG_TASKS_STATS, listener);
 };
 
-/**
- * Creates an instance of {@link PerformanceObserverStats} and starts the
- * observer that records the stats periodically.
- *
- * @returns {void}
- */
-Statistics.prototype.attachLongTasksStats = function() {
-    if (!browser.supportsPerformanceObserver()) {
-        logger.warn('Performance observer for long tasks not supported by browser!');
-
-        return;
-    }
-
-    this.performanceObserverStats = new PerformanceObserverStats(
-        this.eventEmitter,
-        Statistics.longTasksStatsInterval);
-
-    this.conference.on(
-        JitsiConferenceEvents.CONFERENCE_JOINED,
-        () => this.performanceObserverStats.startObserver());
-    this.conference.on(
-        JitsiConferenceEvents.CONFERENCE_LEFT,
-        () => this.performanceObserverStats.stopObserver());
-};
-
 /**
  * Obtains the current value of the LongTasks event statistics.
  *