Allow a received audio codec's payload type to change.

webrtc/api/audio_codecs/audio_format.cc

Index: webrtc/api/audio_codecs/audio_format.cc
diff --git a/webrtc/api/audio_codecs/audio_format.cc b/webrtc/api/audio_codecs/audio_format.cc
index 3a1d0a912dcf8f2a52fd2ec041607953d01bef45..ea5f1839231814fc92cf11b04aed8d3d4e1610d3 100644
--- a/webrtc/api/audio_codecs/audio_format.cc
+++ b/webrtc/api/audio_codecs/audio_format.cc
@@ -45,6 +45,11 @@ SdpAudioFormat::SdpAudioFormat(const std::string& name,
       num_channels(num_channels),
       parameters(param) {}
 
+bool SdpAudioFormat::Matches(const SdpAudioFormat& o) const {
+  return STR_CASE_CMP(name.c_str(), o.name.c_str()) == 0 &&
+         clockrate_hz == o.clockrate_hz && num_channels == o.num_channels;
+}
+
 SdpAudioFormat::~SdpAudioFormat() = default;
 SdpAudioFormat& SdpAudioFormat::operator=(const SdpAudioFormat&) = default;
 SdpAudioFormat& SdpAudioFormat::operator=(SdpAudioFormat&&) = default;