Pass SdpAudioFormat through Channel, without converting to CodecInst

webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc

Index: webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc b/webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc
index 863dcd11770157b33ab9c1efb20e9ccb24556e18..5398aa02b25593ee457887b36a5016537a9e2f91 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module_unittest.cc
@@ -1041,6 +1041,10 @@ TEST_F(AcmReceiverBitExactnessOldApi, 48kHzOutputExternalDecoder) {
     std::vector<AudioCodecSpec> GetSupportedDecoders() override {
       return fact_->GetSupportedDecoders();
     }
+    bool IsSupportedDecoder(const SdpAudioFormat& format) override {
+      return format.name == "MockPCMu" ? true
+                                       : fact_->IsSupportedDecoder(format);
+    }
     std::unique_ptr<AudioDecoder> MakeAudioDecoder(
         const SdpAudioFormat& format) override {
       return format.name == "MockPCMu" ? std::move(mock_decoder_)