Pass SdpAudioFormat through Channel, without converting to CodecInst

webrtc/media/engine/payload_type_mapper.cc

Index: webrtc/media/engine/payload_type_mapper.cc
diff --git a/webrtc/media/engine/payload_type_mapper.cc b/webrtc/media/engine/payload_type_mapper.cc
index 0d449c4e4320872b2bb2674f492877af980838a1..06679198d50861709b1d7a3f6e429a525e7420ae 100644
--- a/webrtc/media/engine/payload_type_mapper.cc
+++ b/webrtc/media/engine/payload_type_mapper.cc
@@ -12,9 +12,16 @@
 
 #include "webrtc/common_types.h"
 #include "webrtc/media/base/mediaconstants.h"
+#include "webrtc/modules/audio_coding/codecs/audio_format.h"
 
 namespace cricket {
 
+webrtc::SdpAudioFormat AudioCodecToSdpAudioFormat(const AudioCodec& ac) {
+  auto params = ac.params;  // Make a copy.
+  return webrtc::SdpAudioFormat(ac.name, ac.clockrate, ac.channels,
+                                std::move(params));
+}
+
 PayloadTypeMapper::PayloadTypeMapper()
     // RFC 3551 reserves payload type numbers in the range 96-127 exclusively
     // for dynamic assignment. Once those are used up, it is recommended that