Build WebRTC with data channel only.

webrtc/pc/channel_audio_nullimpl.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/rtpreceiverinterface.h"
+
+namespace cricket {
+
+class WebRtcVoiceMediaChannel;
+
+std::vector<webrtc::RtpSource> GetSourcesImpl(
+    WebRtcVoiceMediaChannel* media_channel,
+    uint32_t ssrc) {
+  return std::vector<webrtc::RtpSource>();
+}

[pthatcher, 2017/05/18 17:50:26]

Why not stick this in nullaudiofactory.cc?

[Zhi Huang, 2017/05/23 03:40:35]

This would be removed.

+}