Build WebRTC with data channel only.

webrtc/pc/channelmanager.cc

Index: webrtc/pc/channelmanager.cc
diff --git a/webrtc/pc/channelmanager.cc b/webrtc/pc/channelmanager.cc
index af6e3c7e99e16f9780c4872ee8384a2d006e71df..d9dd35a2aa12b9668623c6a6d6b13978a6ded2c3 100644
--- a/webrtc/pc/channelmanager.cc
+++ b/webrtc/pc/channelmanager.cc
@@ -140,14 +140,19 @@ bool ChannelManager::Init() {
         rtc::Bind(&rtc::Thread::SetAllowBlockingCalls, network_thread_, false));
   }
 
+#if defined(HAVE_WEBRTC_VOICE) && defined(HAVE_WEBRTC_VIDEO)
   initialized_ = worker_thread_->Invoke<bool>(
       RTC_FROM_HERE, Bind(&ChannelManager::InitMediaEngine_w, this));
+#else
+  initialized_ = true;
+#endif
   RTC_DCHECK(initialized_);
   return initialized_;
 }
 
 bool ChannelManager::InitMediaEngine_w() {
   RTC_DCHECK(worker_thread_ == rtc::Thread::Current());
+  RTC_DCHECK(media_engine_);
   return media_engine_->Init();
 }
 
@@ -224,6 +229,9 @@ VoiceChannel* ChannelManager::CreateVoiceChannel_w(
   RTC_DCHECK(worker_thread_ == rtc::Thread::Current());
   RTC_DCHECK(nullptr != call);
 
+#ifndef HAVE_WEBRTC_VOICE
+  return nullptr;
+#endif
   VoiceMediaChannel* media_channel = media_engine_->CreateChannel(
       call, media_config, options);
   if (!media_channel)