Bug 1548097 - sort getContributingSources and getSynchronizationSources results r=jib

sort getContributingSources and getSynchronizationSources results

Differential Revision: https://phabricator.services.mozilla.com/D29441

--HG--
extra : moz-landing-system : lando

dom/media/PeerConnection.jsm

@@ -2199,13 +2199,13 @@ class RTCRtpReceiver {
   _getRtpSourcesByType(type) {
     this._fetchRtpSources();
     // Only return the values from within the last 10 seconds as per the spec
-    let cutoffTime = this._rtpSourcesJsTimestamp - 10 * 1000;
-    let sources = [...this._rtpSources.values()].filter(
+    const cutoffTime = this._rtpSourcesJsTimestamp - 10 * 1000;
+    return [...this._rtpSources.values()].filter(
       (entry) => {
         return entry.sourceType == type &&
             (entry.timestamp + entry.sourceClockOffset) >= cutoffTime;
       }).map(e => {
-        let newEntry = {
+        const newEntry = {
           source: e.source,
           timestamp: e.timestamp + e.sourceClockOffset,
           audioLevel: e.audioLevel,
@@ -2214,8 +2214,7 @@ class RTCRtpReceiver {
           Object.assign(newEntry, {voiceActivityFlag: e.voiceActivityFlag});
         }
         return newEntry;
-      });
-      return sources;
+      }).sort((a, b) => b.timestamp - a.timestamp);
   }
 
   getContributingSources() {

dom/media/tests/mochitest/test_peerConnection_audioContributingSources.html

@@ -111,6 +111,24 @@
     is(JSON.stringify(contributingSources),
        JSON.stringify(remoteReceiver.getContributingSources()),
        "getContributingSources is cached");
+    // Check that sources are sorted in descending order by time stamp
+    const timestamp3 = SpWrap(test.pcLocal).mozGetNowInRtpSourceReferenceTime();
+    // Larger offsets are further back in time
+    const testOffsets = [3, 7, 5, 6, 1, 4];
+    for (const offset of testOffsets) {
+      SpWrap(test.pcLocal).mozInsertAudioLevelForContributingSource(
+          localReceiver,
+          offset, // Using offset for SSRC for convenience
+          timestamp3 - offset,
+          true,
+          offset);
+    }
+    const sources = localReceiver.getContributingSources();
+    const sourceOffsets = sources.map(s => s.source);
+    is(JSON.stringify(sourceOffsets),
+       JSON.stringify([...testOffsets].sort((a, b) => a - b)),
+          `Contributing sources are sorted in descending order by timestamp:`
+          + ` ${JSON.stringify(sources)}`);
   };
 
   var test;