AudioCodingModuleImpl: Put CodecManager and Rent-A-Codec in a separate struct

webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h

Index: webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h
index 2a3bc6140591eceeafb5ed27edce662bc18ae34c..3c6d96cc3de95634024d966a178cf0cea66a0868 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.h
@@ -248,10 +248,16 @@ class AudioCodingModuleImpl final : public AudioCodingModule {
   ACMResampler resampler_ GUARDED_BY(acm_crit_sect_);
   AcmReceiver receiver_;  // AcmReceiver has it's own internal lock.
   ChangeLogger bitrate_logger_ GUARDED_BY(acm_crit_sect_);
-  CodecManager codec_manager_ GUARDED_BY(acm_crit_sect_);
-  RentACodec rent_a_codec_ GUARDED_BY(acm_crit_sect_);
 
-  // Last encoder stack obtained from rent_a_codec_.RentEncoderStack.
+  struct EncoderFactory {
+    CodecManager codec_manager;
+    RentACodec rent_a_codec;
+  };
+  rtc::scoped_ptr<EncoderFactory> encoder_factory_ GUARDED_BY(acm_crit_sect_);
+
+  // Current encoder stack, either obtained from
+  // encoder_factory_->rent_a_codec.RentEncoderStack or provided by a call to
+  // RegisterEncoder.
   AudioEncoder* encoder_stack_ GUARDED_BY(acm_crit_sect_);
 
   // This is to keep track of CN instances where we can send DTMFs.