feat(Safari): Add unified plan support for Safari

Enabled desktop sharing and discontinue support for Safari versions prior to 12.1, i.e., the ones with no VP8 support

modules/RTC/RTCUtils.js

     // @see https://github.com/jitsi/lib-jitsi-meet/pull/136
     const isNewStyleConstraintsSupported
         = browser.isFirefox()
-            || browser.isSafariWithVP8()
+            || browser.isSafari()
             || browser.isReactNative();
 
     if (um.indexOf('video') >= 0) {
     isDeviceChangeAvailable(deviceType) {
         return deviceType === 'output' || deviceType === 'audiooutput'
             ? isAudioOutputDeviceChangeAvailable
-            : !browser.isSafariWithVP8();
+            : !browser.isSafari();
     }
 
     /**

modules/RTC/ScreenObtainer.js

 
             // Legacy Firefox
             return this.obtainScreenOnFirefox;
+        } else if (browser.isSafari() && browser.supportsGetDisplayMedia()) {
+            return this.obtainScreenFromGetDisplayMedia;
         }
 
         logger.log(

modules/RTC/TPCUtils.js

     /**
      * Adds a track on the RTCRtpSender as part of the unmute operation.
      * @param {JitsiLocalTrack} localTrack - track to be unmuted.
-     * @returns {boolean} Returns true if the operation is successful,
-     * false otherwise.
+     * @returns {Promise<void>}
      */
     addTrackUnmute(localTrack) {
         const mediaType = localTrack.getType();
 
             return true;
         }
-        transceiver.sender.replaceTrack(track)
+
+        return transceiver.sender.replaceTrack(track)
             .then(() => {
                 this.pc.localTracks.set(localTrack.rtcId, localTrack);
-
-                return true;
-            })
-            .catch(err => {
-                logger.error(`Unmute track failed for ${mediaType} track on ${this.pc}, ${err}`);
-
-                return false;
             });
     }
 
     /**
      * Removes the track from the RTCRtpSender as part of the mute operation.
      * @param {JitsiLocalTrack} localTrack - track to be removed.
-     * @returns {boolean} Returns true if the operation is successful,
-     * false otherwise.
+     * @returns {Promise<void>}
      */
     removeTrackMute(localTrack) {
         const mediaType = localTrack.getType();
         }
 
         logger.debug(`Removing ${localTrack} on ${this.pc}`);
-        transceiver.sender.replaceTrack(null)
+
+        return transceiver.sender.replaceTrack(null)
             .then(() => {
                 this.pc.localTracks.delete(localTrack.rtcId);
-                this.pc.localSSRCs.delete(localTrack.rtcId);
-
-                return true;
-            })
-            .catch(err => {
-                logger.error(`Mute track failed for ${mediaType} track on ${this.pc}, ${err}`);
-
-                return false;
             });
     }
 

modules/RTC/TraceablePeerConnection.js

  * the renegotiation is required or <tt>false</tt> otherwise.
  */
 TraceablePeerConnection.prototype.addTrackUnmute = function(track) {
+    if (browser.usesUnifiedPlan()) {
+        return this.tpcUtils.addTrackUnmute(track);
+    }
     if (!this._assertTrackBelongs('addTrackUnmute', track)) {
         // Abort
         return false;
     }
 
     logger.info(`Adding ${track} as unmute to ${this}`);
-    if (browser.usesUnifiedPlan()) {
-        return this.tpcUtils.addTrackUnmute(track);
-    }
     const webRtcStream = track.getOriginalStream();
 
     if (!webRtcStream) {
  * changed and the renegotiation is required or <tt>false</tt> otherwise.
  */
 TraceablePeerConnection.prototype.removeTrackMute = function(localTrack) {
+    if (browser.usesUnifiedPlan()) {
+        return this.tpcUtils.removeTrackMute(localTrack);
+    }
     const webRtcStream = localTrack.getOriginalStream();
 
     this.trace(
         // Abort - nothing to be done here
         return false;
     }
-    if (browser.usesUnifiedPlan()) {
-        return this.tpcUtils.removeTrackMute(localTrack);
-    }
     if (webRtcStream) {
         logger.info(
             `Removing ${localTrack} as mute from ${this}`);
     // TODO (brian): After moving all browsers to adapter, check if adapter is
     // accounting for different getStats apis, making the browser-checking-if
     // unnecessary.
-    if (browser.isSafariWithWebrtc() || browser.isFirefox()
-            || browser.isReactNative()) {
+    if (browser.isSafari() || browser.isFirefox() || browser.isReactNative()) {
         // uses the new Promise based getStats
         this.peerconnection.getStats()
             .then(callback)

modules/browser/BrowserCapabilities.js

      * strategy or <tt>false</tt> otherwise.
      */
     doesVideoMuteByStreamRemove() {
-        return this.isChromiumBased();
+        return this.isChromiumBased() || this.isSafari();
     }
 
     /**
             || this.isOpera();
     }
 
-    /**
-     * Checks if current browser is a Safari and a version of Safari that
-     * supports native webrtc.
-     *
-     * @returns {boolean}
-     */
-    isSafariWithWebrtc() {
-        return this.isSafari()
-            && !this.isVersionLessThan('11');
-    }
-
-    /**
-     * Checks if current browser is a Safari and a version of Safari that
-     * supports VP8.
-     *
-     * @returns {boolean}
-     */
-    isSafariWithVP8() {
-        return this.isSafari()
-            && !this.isVersionLessThan('12.1');
-    }
-
     /**
      * Checks if the current browser is supported.
      *
         return this.isChromiumBased()
             || this.isFirefox()
             || this.isReactNative()
-            || this.isSafariWithWebrtc();
+            || (this.isSafari() && !this.isVersionLessThan('12.1'));
     }
 
     /**
      * otherwise.
      */
     supportsVideoMuteOnConnInterrupted() {
-        return this.isChromiumBased() || this.isReactNative()
-            || this.isSafariWithVP8();
+        return this.isChromiumBased() || this.isReactNative() || this.isSafari();
     }
 
     /**
     supportsBandwidthStatistics() {
         // FIXME bandwidth stats are currently not implemented for FF on our
         // side, but not sure if not possible ?
-        return !this.isFirefox() && !this.isSafariWithWebrtc();
+        return !this.isFirefox() && !this.isSafari();
     }
 
     /**
      * candidates through the legacy getStats() API.
      */
     supportsLocalCandidateRttStatistics() {
-        return this.isChromiumBased() || this.isReactNative()
-            || this.isSafariWithVP8();
+        return this.isChromiumBased() || this.isReactNative() || this.isSafari();
     }
 
     /**
      * @returns {boolean}
      */
     supportsRtpSender() {
-        return this.isFirefox() || this.isSafariWithVP8();
+        return this.isFirefox() || this.isSafari();
     }
 
     /**
      * @returns {boolean}
      */
     supportsRtx() {
-        return !this.isFirefox() && !this.usesUnifiedPlan();
+        return !this.isFirefox();
     }
 
     /**
      * @returns {boolean}
      */
     supportsVideo() {
-        // FIXME: Check if we can use supportsVideoOut and supportsVideoIn. I
-        // leave the old implementation here in order not to brake something.
-
-        // Older versions of Safari using webrtc/adapter do not support video
-        // due in part to Safari only supporting H264 and the bridge sending VP8
-        // Newer Safari support VP8 and other WebRTC features.
-        return !this.isSafariWithWebrtc()
-            || (this.isSafariWithVP8() && this.usesPlanB());
+        return true;
     }
 
     /**
      * @returns {boolean}
      */
     usesSdpMungingForSimulcast() {
-        return this.isChromiumBased() || this.isSafariWithVP8();
+        return this.isChromiumBased() || this.isSafari();
     }
 
     /**
             return true;
         }
 
-        if (this.isSafariWithVP8() && typeof window.RTCRtpTransceiver !== 'undefined') {
+        if (this.isSafari() && typeof window.RTCRtpTransceiver !== 'undefined') {
             // eslint-disable-next-line max-len
             // https://trac.webkit.org/changeset/236144/webkit/trunk/LayoutTests/webrtc/video-addLegacyTransceiver.html
             // eslint-disable-next-line no-undef
             return !this.isVersionLessThan(REQUIRED_CHROME_VERSION);
         }
 
-        if (this.isFirefox() || this.isSafariWithWebrtc()) {
+        if (this.isFirefox() || this.isSafari()) {
             return true;
         }
 

modules/statistics/RTPStatsCollector.js

      * @type {boolean}
      */
     this._usesPromiseGetStats
-        = browser.isSafariWithWebrtc() || browser.isFirefox();
+        = browser.isSafari() || browser.isFirefox();
 
     /**
      * The function which is to be used to retrieve the value associated in a