fix(Jingle): stop reverting the SSRCs from Firefox

modules/RTC/TraceablePeerConnection.js

@@ -1482,11 +1482,6 @@ TraceablePeerConnection.prototype._injectSsrcGroupForUnifiedSimulcast
                 return desc;
             }
 
-            // Reverse the order of the SSRCs when signaling them to the bridge. On Firefox, the first SSRC corresponds
-            // to the highest resolution stream whereas the bridge assumes it to be that of the lowest resolution
-            // stream as is the case with the other browsers.
-            browser.isFirefox() && ssrcs.reverse();
-
             video.ssrcGroups.push({
                 semantics: 'SIM',
                 ssrcs: ssrcs.join(' ')

modules/sdp/SDP.js

@@ -143,16 +143,10 @@ SDP.prototype.toJingle = function(elem, thecreator) {
         }
 
         let ssrc;
-        const simGroup = SDPUtil.findLine(this.media[i], 'a=ssrc-group:SIM');
         const assrcline = SDPUtil.findLine(this.media[i], 'a=ssrc:');
 
         if (assrcline) {
-            if (browser.isFirefox() && simGroup) {
-                // Use the first ssrc from the SIM group since the order of the SSRCs need to be reversed for Firefox.
-                ssrc = simGroup.substring(17).split(' ')[0];
-            } else {
-                ssrc = assrcline.substring(7).split(' ')[0]; // take the first
-            }
+            ssrc = assrcline.substring(7).split(' ')[0]; // take the first
         } else {
             ssrc = false;
         }