Revert of Adding "first packet received" notification to PeerConnectionObserver.

talk/app/webrtc/peerconnection.cc

 /*
  * libjingle
  * Copyright 2012 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 645 matching lines @@
   session_->SignalVoiceChannelDestroyed.connect(
       this, &PeerConnection::OnVoiceChannelDestroyed);
   session_->SignalVideoChannelDestroyed.connect(
       this, &PeerConnection::OnVideoChannelDestroyed);
   session_->SignalDataChannelCreated.connect(
       this, &PeerConnection::OnDataChannelCreated);
   session_->SignalDataChannelDestroyed.connect(
       this, &PeerConnection::OnDataChannelDestroyed);
   session_->SignalDataChannelOpenMessage.connect(
       this, &PeerConnection::OnDataChannelOpenMessage);
-  session_->SignalFirstMediaPacketReceived.connect(
-      this, &PeerConnection::OnFirstMediaPacketReceived);
   return true;
 }
 
 rtc::scoped_refptr<StreamCollectionInterface>
 PeerConnection::local_streams() {
   return local_streams_;
 }
 
 rtc::scoped_refptr<StreamCollectionInterface>
 PeerConnection::remote_streams() {
@@ skipping 1273 matching lines @@
       InternalCreateDataChannel(label, &config));
   if (!channel.get()) {
     LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message.";
     return;
   }
 
   observer_->OnDataChannel(
       DataChannelProxy::Create(signaling_thread(), channel));
 }
 
-void PeerConnection::OnFirstMediaPacketReceived() {
-  RTC_DCHECK(signaling_thread()->IsCurrent());
-  observer_->OnFirstMediaPacketReceived();
-}
-
 RtpSenderInterface* PeerConnection::FindSenderById(const std::string& id) {
   auto it =
       std::find_if(senders_.begin(), senders_.end(),
                    [id](const rtc::scoped_refptr<RtpSenderInterface>& sender) {
                      return sender->id() == id;
                    });
   return it != senders_.end() ? it->get() : nullptr;
 }
 
 std::vector<rtc::scoped_refptr<RtpSenderInterface>>::iterator
@@ skipping 46 matching lines @@
 DataChannel* PeerConnection::FindDataChannelBySid(int sid) const {
   for (const auto& channel : sctp_data_channels_) {
     if (channel->id() == sid) {
       return channel;
     }
   }
   return nullptr;
 }
 
 }  // namespace webrtc