Build WebRTC with data channel only.

webrtc/pc/webrtcsession.cc

 /*
  *  Copyright 2012 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.
  */
 
@@ skipping 1883 matching lines @@
   SignalDataChannelCreated();
 
   return true;
 }
 
 Call::Stats WebRtcSession::GetCallStats() {
   if (!worker_thread()->IsCurrent()) {
     return worker_thread()->Invoke<Call::Stats>(
         RTC_FROM_HERE, rtc::Bind(&WebRtcSession::GetCallStats, this));
   }
-  RTC_DCHECK(call_);
+  if (!call_)
+    return Call::Stats();
   return call_->GetStats();
 }
 
 std::unique_ptr<SessionStats> WebRtcSession::GetStats_n(
     const ChannelNamePairs& channel_name_pairs) {
   RTC_DCHECK(network_thread()->IsCurrent());
   std::unique_ptr<SessionStats> session_stats(new SessionStats());
   for (const auto channel_name_pair : { &channel_name_pairs.voice,
                                         &channel_name_pairs.video,
                                         &channel_name_pairs.data }) {
@@ skipping 484 matching lines @@
       (rtp_data_channel_->rtcp_dtls_transport() != nullptr);
   channel_manager_->DestroyRtpDataChannel(rtp_data_channel_.release());
   transport_controller_->DestroyDtlsTransport(
       transport_name, cricket::ICE_CANDIDATE_COMPONENT_RTP);
   if (need_to_delete_rtcp) {
     transport_controller_->DestroyDtlsTransport(
         transport_name, cricket::ICE_CANDIDATE_COMPONENT_RTCP);
   }
 }
 }  // namespace webrtc