feat(ssrc-rewriting) Add a flag to signal support for ssrc re-writing to Jicofo.

modules/flags/FeatureFlags.js

     init(flags) {
         this._sourceNameSignaling = Boolean(flags.sourceNameSignaling);
         this._sendMultipleVideoStreams = Boolean(flags.sendMultipleVideoStreams);
+        this._ssrcRewriting = Boolean(flags.ssrcRewritingOnBridgeSupported);
 
         // For Chromium, check if Unified plan is enabled.
         this._usesUnifiedPlan = browser.supportsUnifiedPlan()
 
         logger.info(`Source name signaling: ${this._sourceNameSignaling},`
             + ` Send multiple video streams: ${this._sendMultipleVideoStreams},`
+            + ` SSRC rewriting supported: ${this._ssrcRewriting},`
             + ` uses Unified plan: ${this._usesUnifiedPlan}`);
     }
 
     isSourceNameSignalingEnabled() {
         return this._sourceNameSignaling;
     }
+
+    /**
+     * Checks if the clients supports re-writing of the SSRCs on the media streams by the bridge.
+     * @returns {boolean}
+     */
+    isSsrcRewritingSupported() {
+        return this._ssrcRewriting;
+    }
 }
 
 export default new FeatureFlags();

modules/xmpp/xmpp.js

             logger.info('Source-name signaling is enabled');
             this.caps.addFeature('http://jitsi.org/source-name');
         }
+
+        if (FeatureFlags.isSsrcRewritingSupported()) {
+            logger.info('SSRC rewriting is supported');
+            this.caps.addFeature('http://jitsi.org/ssrc-rewriting');
+        }
     }
 
     /**

types/auto/modules/flags/FeatureFlags.d.ts

     init(flags: any): void;
     _sourceNameSignaling: boolean;
     _sendMultipleVideoStreams: boolean;
+    _ssrcRewriting: boolean;
     _usesUnifiedPlan: any;
     /**
      * Checks if multiple local video streams support is enabled.
      * @returns {boolean}
      */
     isSourceNameSignalingEnabled(): boolean;
+    /**
+     * Checks if the clients supports re-writing of the SSRCs on the media streams by the bridge.
+     * @returns {boolean}
+     */
+    isSsrcRewritingSupported(): boolean;
 }