Build WebRTC with data channel only.

webrtc/pc/peerconnectionfactory_audio.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/audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/audio_encoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_encoder_factory.h"
+#include "webrtc/base/scoped_ref_ptr.h"

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

I think a good name for this file may be audiofactory.cc

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

Done.

+
+namespace webrtc {
+
+rtc::scoped_refptr<AudioEncoderFactory> CreateBuiltinAudioEncoderFactoryImpl() {
+  return CreateBuiltinAudioEncoderFactory();
+}
+
+rtc::scoped_refptr<AudioDecoderFactory> CreateBuiltinAudioDecoderFactoryImpl() {
+  return CreateBuiltinAudioDecoderFactory();
+}
+
+}  // namespace webrtc