Forward the SignalFirstPacketReceived to RtpReceiver.

webrtc/api/webrtcsession.cc

Index: webrtc/api/webrtcsession.cc
diff --git a/webrtc/api/webrtcsession.cc b/webrtc/api/webrtcsession.cc
index a7c712c6a1f8c407f74d41992aeb6def83cf8634..b9a3fc8453389dc040a28f51a47d0a4649e0eb49 100644
--- a/webrtc/api/webrtcsession.cc
+++ b/webrtc/api/webrtcsession.cc
@@ -1767,6 +1767,8 @@ bool WebRtcSession::CreateVoiceChannel(const cricket::ContentInfo* content,
 
   voice_channel_->SignalDtlsSetupFailure.connect(
       this, &WebRtcSession::OnDtlsSetupFailure);
+  voice_channel_->SignalFirstPacketReceived.connect(
+      this, &WebRtcSession::OnChannelFirstPacketReceived);
 
   SignalVoiceChannelCreated();
   voice_channel_->SignalSentPacket.connect(this,
@@ -1790,6 +1792,8 @@ bool WebRtcSession::CreateVideoChannel(const cricket::ContentInfo* content,
   }
   video_channel_->SignalDtlsSetupFailure.connect(
       this, &WebRtcSession::OnDtlsSetupFailure);
+  video_channel_->SignalFirstPacketReceived.connect(
+      this, &WebRtcSession::OnChannelFirstPacketReceived);
 
   SignalVideoChannelCreated();
   video_channel_->SignalSentPacket.connect(this,
@@ -1831,6 +1835,21 @@ void WebRtcSession::OnDtlsSetupFailure(cricket::BaseChannel*, bool rtcp) {
            rtcp ? kDtlsSetupFailureRtcp : kDtlsSetupFailureRtp);
 }
 
+void WebRtcSession::OnChannelFirstPacketReceived(
+    cricket::BaseChannel* channel) {
+  ASSERT(signaling_thread()->IsCurrent());
+
+  if (!received_first_audio_packet_ &&
+      channel->media_type() == cricket::MEDIA_TYPE_AUDIO) {
+    received_first_audio_packet_ = true;
+    SignalFirstAudioPacketReceived();
+  } else if (!received_first_video_packet_ &&
+             channel->media_type() == cricket::MEDIA_TYPE_VIDEO) {
+    received_first_video_packet_ = true;
+    SignalFirstVideoPacketReceived();
+  }
+}
+
 void WebRtcSession::OnDataChannelMessageReceived(
     cricket::DataChannel* channel,
     const cricket::ReceiveDataParams& params,