Bug 1433005 - Simplify codec pruning in NegotiateCodecs; r=bwc

--HG--
extra : rebase_source : dd40820b009cb8dc3cff74bbaee9a1d3dbe2a0dc

media/webrtc/signaling/src/jsep/JsepTrack.cpp

@@ -486,21 +486,25 @@ JsepTrack::NegotiateCodecs(
 
   // TODO(bug 814227): Remove this once we're ready to put multiple codecs in an
   // answer.  For now, remove all but the first codec unless the red codec
-  // exists, and then we include the others per RFC 5109, section 14.2.
-  // Note: now allows keeping the telephone-event codec, if it appears, as the
-  // last codec in the list.
+  // exists, in which case we include the others per RFC 5109, section 14.2.
   if (!codecs->empty() && !red) {
-    int newSize = dtmf ? 2 : 1;
-    for (size_t i = 1; i < codecs->size(); ++i) {
-      if (!dtmf || dtmf != (*codecs)[i]) {
-        delete (*codecs)[i];
-        (*codecs)[i] = nullptr;
+    std::vector<JsepCodecDescription*> codecsToKeep;
+
+    bool foundPreferredCodec = false;
+    for (auto codec: *codecs) {
+      if (codec == dtmf) {
+        codecsToKeep.push_back(codec);
+      } else if (codec == ulpfec) {
+        codecsToKeep.push_back(codec);
+      } else if (!foundPreferredCodec) {
+        codecsToKeep.insert(codecsToKeep.begin(), codec);
+        foundPreferredCodec = true;
+      } else {
+        delete codec;
       }
     }
-    if (dtmf) {
-      (*codecs)[newSize-1] = dtmf;
-    }
-    codecs->resize(newSize);
+
+    *codecs = codecsToKeep;
   }
 }