Removing `preference` field from `cricket::Codec`.

webrtc/pc/mediasession.cc

Index: webrtc/pc/mediasession.cc
diff --git a/webrtc/pc/mediasession.cc b/webrtc/pc/mediasession.cc
index a9d1b95c22aee6aae9299315a9ecc05586242336..a6abb650080d7d5e2c152cab5a3a43352ac868a8 100644
--- a/webrtc/pc/mediasession.cc
+++ b/webrtc/pc/mediasession.cc
@@ -749,7 +749,6 @@ static bool CreateMediaContentOffer(
     StreamParamsVec* current_streams,
     MediaContentDescriptionImpl<C>* offer) {
   offer->AddCodecs(codecs);
-  offer->SortCodecs();
 
   if (secure_policy == SEC_REQUIRED) {
     offer->set_crypto_required(CT_SDES);
@@ -810,6 +809,8 @@ static void NegotiateCodecs(const std::vector<C>& local_codecs,
                             std::vector<C>* negotiated_codecs) {
   for (const C& ours : local_codecs) {
     C theirs;
+    // Note that we intentionally only find one matching codec for each of our
+    // local codecs, in case the remote offer contains duplicate codecs.
     if (FindMatchingCodec(local_codecs, offered_codecs, ours, &theirs)) {
       C negotiated = ours;
       negotiated.IntersectFeedbackParams(theirs);
@@ -822,14 +823,24 @@ static void NegotiateCodecs(const std::vector<C>& local_codecs,
                             offered_apt_value);
       }
       negotiated.id = theirs.id;
-      // RFC3264: Although the answerer MAY list the formats in their desired
-      // order of preference, it is RECOMMENDED that unless there is a
-      // specific reason, the answerer list formats in the same relative order
-      // they were present in the offer.
-      negotiated.preference = theirs.preference;
       negotiated_codecs->push_back(negotiated);
     }
   }
+  // RFC3264: Although the answerer MAY list the formats in their desired
+  // order of preference, it is RECOMMENDED that unless there is a
+  // specific reason, the answerer list formats in the same relative order
+  // they were present in the offer.
+  std::vector<int> offer_payload_types;
+  for (const C& codec : offered_codecs) {
+    offer_payload_types.push_back(codec.id);
+  }
+  std::sort(negotiated_codecs->begin(), negotiated_codecs->end(),
+            [offer_payload_types](const C& a, const C& b) {
+              return std::find(offer_payload_types.begin(),
+                               offer_payload_types.end(), a.id) <
+                     std::find(offer_payload_types.begin(),
+                               offer_payload_types.end(), b.id);
+            });

[pthatcher1, 2016/04/12 00:35:19]

If you're going to fix the sort in one place, you should probably fix it in
both.

[Taylor Brandstetter, 2016/04/12 01:23:29]

Done.

 }
 
 // Finds a codec in |codecs2| that matches |codec_to_match|, which is
@@ -1042,7 +1053,6 @@ static bool CreateMediaContentAnswer(
   std::vector<C> negotiated_codecs;
   NegotiateCodecs(local_codecs, offer->codecs(), &negotiated_codecs);
   answer->AddCodecs(negotiated_codecs);
-  answer->SortCodecs();
   answer->set_protocol(offer->protocol());
   RtpHeaderExtensions negotiated_rtp_extensions;
   NegotiateRtpHeaderExtensions(local_rtp_extenstions,
@@ -1365,8 +1375,8 @@ SessionDescription* MediaSessionDescriptionFactory::CreateAnswer(
     const SessionDescription* offer, const MediaSessionOptions& options,
     const SessionDescription* current_description) const {
   // The answer contains the intersection of the codecs in the offer with the
-  // codecs we support, ordered by our local preference. As indicated by
-  // XEP-0167, we retain the same payload ids from the offer in the answer.
+  // codecs we support. As indicated by XEP-0167, we retain the same payload ids
+  // from the offer in the answer.
   std::unique_ptr<SessionDescription> answer(new SessionDescription());
 
   StreamParamsVec current_streams;