Starting with patch 34 from https://codereview.webrtc.org/2854123003/

webrtc/pc/createpeerconnectionfactory.cc

+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_encoder_factory.h"
+#include "webrtc/api/peerconnectioninterface.h"
+#include "webrtc/base/bind.h"
+#include "webrtc/base/scoped_ref_ptr.h"
+#include "webrtc/base/thread.h"
+#include "webrtc/call/callfactoryinterface.h"
+#include "webrtc/logging/rtc_event_log/rtc_event_log_factory_interface.h"
+#include "webrtc/media/engine/webrtcmediaengine.h"
+
+namespace webrtc {
+
+rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
+    rtc::scoped_refptr<AudioEncoderFactory> audio_encoder_factory,
+    rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory) {
+  return CreatePeerConnectionFactoryWithAudioMixer(
+      nullptr /*network_thread*/,
+      nullptr /*worker_thread*/, nullptr /*signaling_thread*/,
+      nullptr /*default_adm*/, audio_encoder_factory, audio_decoder_factory,
+      nullptr /*video_encoder_factory*/, nullptr /*video_decoder_factory*/,
+      nullptr /*audio_mixer*/);
+}
+
+rtc::scoped_refptr<PeerConnectionFactoryInterface>
+CreatePeerConnectionFactory() {
+  return CreatePeerConnectionFactory(CreateBuiltinAudioEncoderFactory(),
+                                     CreateBuiltinAudioDecoderFactory());
+}
+
+// Note: all the other CreatePeerConnectionFactory variants just end up calling
+// this, ultimately.
+rtc::scoped_refptr<PeerConnectionFactoryInterface>
+CreatePeerConnectionFactoryWithAudioMixer(
+    rtc::Thread* network_thread,
+    rtc::Thread* worker_thread,
+    rtc::Thread* signaling_thread,
+    AudioDeviceModule* default_adm,
+    rtc::scoped_refptr<AudioEncoderFactory> audio_encoder_factory,
+    rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory,
+    cricket::WebRtcVideoEncoderFactory* video_encoder_factory,
+    cricket::WebRtcVideoDecoderFactory* video_decoder_factory,
+    rtc::scoped_refptr<AudioMixer> audio_mixer) {
+  std::unique_ptr<cricket::MediaEngineInterface> media_engine(
+        cricket::WebRtcMediaEngineFactory::Create(
+            default_adm, audio_encoder_factory, audio_decoder_factory,
+            video_encoder_factory, video_decoder_factory, audio_mixer));
+
+  std::unique_ptr<CallFactoryInterface> call_factory = CreateCallFactory();
+
+  std::unique_ptr<RtcEventLogFactoryInterface> event_log_factory =
+      CreateRtcEventLogFactory();
+
+  return CreateModularPeerConnectionFactory(
+      network_thread, worker_thread, signaling_thread, default_adm,
+      audio_encoder_factory, audio_decoder_factory, video_encoder_factory,
+      video_decoder_factory, audio_mixer, std::move(media_engine),
+      std::move(call_factory), std::move(event_log_factory));
+}
+
+rtc::scoped_refptr<PeerConnectionFactoryInterface>
+CreatePeerConnectionFactoryWithAudioMixer(
+    rtc::Thread* network_thread,
+    rtc::Thread* worker_thread,
+    rtc::Thread* signaling_thread,
+    AudioDeviceModule* default_adm,
+    cricket::WebRtcVideoEncoderFactory* encoder_factory,
+    cricket::WebRtcVideoDecoderFactory* decoder_factory,
+    rtc::scoped_refptr<AudioMixer> audio_mixer) {
+  return CreatePeerConnectionFactoryWithAudioMixer(
+      network_thread, worker_thread, signaling_thread, default_adm,
+      CreateBuiltinAudioEncoderFactory(), CreateBuiltinAudioDecoderFactory(),
+      encoder_factory, decoder_factory, audio_mixer);
+}
+
+rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
+    rtc::Thread* network_thread,
+    rtc::Thread* worker_thread,
+    rtc::Thread* signaling_thread,
+    AudioDeviceModule* default_adm,
+    cricket::WebRtcVideoEncoderFactory* encoder_factory,
+    cricket::WebRtcVideoDecoderFactory* decoder_factory) {
+  return CreatePeerConnectionFactoryWithAudioMixer(
+      network_thread, worker_thread, signaling_thread, default_adm,
+      encoder_factory, decoder_factory, nullptr);
+}
+
+rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
+    rtc::Thread* network_thread,
+    rtc::Thread* worker_thread,
+    rtc::Thread* signaling_thread,
+    AudioDeviceModule* default_adm,
+    rtc::scoped_refptr<AudioEncoderFactory> audio_encoder_factory,
+    rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory,
+    cricket::WebRtcVideoEncoderFactory* video_encoder_factory,
+    cricket::WebRtcVideoDecoderFactory* video_decoder_factory) {
+  return CreatePeerConnectionFactoryWithAudioMixer(
+      network_thread, worker_thread, signaling_thread, default_adm,
+      audio_encoder_factory, audio_decoder_factory, video_encoder_factory,
+      video_decoder_factory, nullptr);
+}
+
+}  // namespace webrtc