AcmReceiver: Eliminate AcmReceiver::decoders_

webrtc/modules/audio_coding/codecs/audio_format.cc

Index: webrtc/modules/audio_coding/codecs/audio_format.cc
diff --git a/webrtc/modules/audio_coding/codecs/audio_format.cc b/webrtc/modules/audio_coding/codecs/audio_format.cc
index 86d5d800422893f95e55f2e890468e4cc4a9448e..ebd7cb030b4fdbcec19eaef2cbc09cff856ec376 100644
--- a/webrtc/modules/audio_coding/codecs/audio_format.cc
+++ b/webrtc/modules/audio_coding/codecs/audio_format.cc
@@ -10,6 +10,8 @@
 
 #include "webrtc/modules/audio_coding/codecs/audio_format.h"
 
+#include "webrtc/common_types.h"
+
 namespace webrtc {
 
 SdpAudioFormat::SdpAudioFormat(const SdpAudioFormat&) = default;
@@ -33,6 +35,12 @@ SdpAudioFormat::~SdpAudioFormat() = default;
 SdpAudioFormat& SdpAudioFormat::operator=(const SdpAudioFormat&) = default;
 SdpAudioFormat& SdpAudioFormat::operator=(SdpAudioFormat&&) = default;
 
+bool operator==(const SdpAudioFormat& a, const SdpAudioFormat& b) {
+  return STR_CASE_CMP(a.name.c_str(), b.name.c_str()) == 0 &&
+         a.clockrate_hz == b.clockrate_hz && a.num_channels == b.num_channels &&
+         a.parameters == b.parameters;
+}
+
 void swap(SdpAudioFormat& a, SdpAudioFormat& b) {
   using std::swap;
   swap(a.name, b.name);