Pass ownership of external encoders to the ACM

webrtc/modules/audio_coding/acm2/codec_manager.h

Index: webrtc/modules/audio_coding/acm2/codec_manager.h
diff --git a/webrtc/modules/audio_coding/acm2/codec_manager.h b/webrtc/modules/audio_coding/acm2/codec_manager.h
index 660a9c0fa024f1ff2573821efe896214e89adbce..fbd3a18b188efa203949159bf0e0b8c9bde353b3 100644
--- a/webrtc/modules/audio_coding/acm2/codec_manager.h
+++ b/webrtc/modules/audio_coding/acm2/codec_manager.h
@@ -41,6 +41,9 @@ class CodecManager final {
   const CodecInst* GetCodecInst() const {
     return send_codec_inst_ ? &*send_codec_inst_ : nullptr;
   }
+
+  void UnsetCodecInst() { send_codec_inst_ = rtc::Optional<CodecInst>(); }
+
   const RentACodec::StackParameters* GetStackParams() const {
     return &codec_stack_params_;
   }