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 be5e2c56dd977070a4b4445778399c7d3b41d3ab..574b15ddc8393e9db8fa27f4567f1fb0d2fe405f 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_)