Build WebRTC with data channel only.

webrtc/pc/peerconnectionfactory.cc

Index: webrtc/pc/peerconnectionfactory.cc
diff --git a/webrtc/pc/peerconnectionfactory.cc b/webrtc/pc/peerconnectionfactory.cc
index 2c3dd11fee43c08a7e1d5b4ba78527f7b941372d..071180bd02c1b613bf68044b401284dc0d4b7a7e 100644
--- a/webrtc/pc/peerconnectionfactory.cc
+++ b/webrtc/pc/peerconnectionfactory.cc
@@ -56,8 +56,14 @@ rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
 
 rtc::scoped_refptr<PeerConnectionFactoryInterface>
 CreatePeerConnectionFactory() {
-  return CreatePeerConnectionFactory(CreateBuiltinAudioEncoderFactory(),
-                                     CreateBuiltinAudioDecoderFactory());
+  rtc::scoped_refptr<AudioEncoderFactory> audio_encoder_factory;
+  rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory;
+#ifdef HAVE_MEDIA
+  audio_encoder_factory = CreateBuiltinAudioEncoderFactory();
+  audio_decoder_factory = CreateBuiltinAudioDecoderFactory();
+#endif
+  return CreatePeerConnectionFactory(audio_encoder_factory,
+                                     audio_decoder_factory);
 }
 
 rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
@@ -125,10 +131,16 @@ CreatePeerConnectionFactoryWithAudioMixer(
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     cricket::WebRtcVideoDecoderFactory* decoder_factory,
     rtc::scoped_refptr<AudioMixer> audio_mixer) {
+  rtc::scoped_refptr<AudioEncoderFactory> audio_encoder_factory;
+  rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory;
+#ifdef HAVE_MEDIA
+  audio_encoder_factory = CreateBuiltinAudioEncoderFactory();
+  audio_decoder_factory = CreateBuiltinAudioDecoderFactory();
+#endif
   return CreatePeerConnectionFactoryWithAudioMixer(
       network_thread, worker_thread, signaling_thread, default_adm,
-      CreateBuiltinAudioEncoderFactory(), CreateBuiltinAudioDecoderFactory(),
-      encoder_factory, decoder_factory, audio_mixer);
+      audio_encoder_factory, audio_decoder_factory, encoder_factory,
+      decoder_factory, audio_mixer);
 }
 
 PeerConnectionFactory::PeerConnectionFactory(
@@ -389,12 +401,15 @@ rtc::Thread* PeerConnectionFactory::network_thread() {
 std::unique_ptr<cricket::MediaEngineInterface>
 PeerConnectionFactory::CreateMediaEngine_w() {
   RTC_DCHECK(worker_thread_ == rtc::Thread::Current());
+#ifdef HAVE_MEDIA
   return std::unique_ptr<cricket::MediaEngineInterface>(
       cricket::WebRtcMediaEngineFactory::Create(
-          default_adm_.get(), audio_encoder_factory_,
-          audio_decoder_factory_,
+          default_adm_.get(), audio_encoder_factory_, audio_decoder_factory_,
           video_encoder_factory_.get(), video_decoder_factory_.get(),
           external_audio_mixer_));
+#else
+  return std::unique_ptr<cricket::MediaEngineInterface>();
+#endif

[pthatcher1, 2017/05/03 18:05:53]

Why not just not call CreateMediaEngine_w from
PeerConnectionFactory::Initialize()?

[Zhi Huang, 2017/05/04 01:08:03]

The idea here is trying to avoid compiling and linking the method
WebRtcMediaFactory::Create(). It seems that not calling it from Initialize()
doesn't help.

[pthatcher1, 2017/05/05 01:45:12]

Ah, duh.  You're right.

 }
 
 }  // namespace webrtc