Audio codec implementations: Take optional codec ID argument

None of the built-in codecs do anything with the ID, but callers will
soon require them to accept it.

Bug: webrtc:8941
Change-Id: I0eb77db82d72c7d34cff639fecb67c1e6ec421bf
Reviewed-on: https://webrtc-review.googlesource.com/58089
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22259}
diff --git a/api/audio_codecs/opus/audio_decoder_opus.cc b/api/audio_codecs/opus/audio_decoder_opus.cc
index 472a079..73a0a3f 100644
--- a/api/audio_codecs/opus/audio_decoder_opus.cc
+++ b/api/audio_codecs/opus/audio_decoder_opus.cc
@@ -55,7 +55,8 @@
 }
 
 std::unique_ptr<AudioDecoder> AudioDecoderOpus::MakeAudioDecoder(
-    Config config) {
+    Config config,
+    rtc::Optional<AudioCodecPairId> /*codec_pair_id*/) {
   return rtc::MakeUnique<AudioDecoderOpusImpl>(config.num_channels);
 }