Revert of Modify PeerConnection for end-to-end QuicDataChannel usage (patchset #4 id:60001 of https://codereview.webrtc.org/2089553002/ )

Reason for revert:
Reverting because description was inaccurate. Will reland after updating description.

Original issue's description:
> Modify PeerConnection for end-to-end QuicDataChannel usage
>
> To allow end-to-end QuicDataChannel usage with a
> PeerConnection, RTCConfiguration has been modified to
> include a boolean for whether to do QUIC, since negotiation of
> QUIC is not implemented. If one peer does QUIC, then it will be
> assumed that the other peer must do QUIC or the connection
> will fail.
>
> PeerConnection has been modified to create data channels of type
> QuicDataChannel when the peer wants to do QUIC.
>
> WebRtcSession has been modified to use a QuicTransportChannel
> instead of a DtlsTransportChannelWrapper/DataChannel
> when QUIC should be used.
>
> Modification of previous in-flight CL: https://codereview.chromium.org/1844803002/
>
> Committed: https://crrev.com/36c8d69ce188102ae6fd48c371cf1518f08698fb
> Cr-Commit-Position: refs/heads/master@{#13470}

TBR=pthatcher@webrtc.org,zhihuang@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.webrtc.org/2146133002
Cr-Commit-Position: refs/heads/master@{#13471}
diff --git a/webrtc/api/quicdatachannel.cc b/webrtc/api/quicdatachannel.cc
index 5493382..f4f5732 100644
--- a/webrtc/api/quicdatachannel.cc
+++ b/webrtc/api/quicdatachannel.cc
@@ -61,12 +61,10 @@
 
 QuicDataChannel::QuicDataChannel(rtc::Thread* signaling_thread,
                                  rtc::Thread* worker_thread,
-                                 rtc::Thread* network_thread,
                                  const std::string& label,
                                  const DataChannelInit& config)
     : signaling_thread_(signaling_thread),
       worker_thread_(worker_thread),
-      network_thread_(network_thread),
       id_(config.id),
       state_(kConnecting),
       buffered_amount_(0),
@@ -93,12 +91,12 @@
                   << " is not open so cannot send.";
     return false;
   }
-  return network_thread_->Invoke<bool>(
-      RTC_FROM_HERE, rtc::Bind(&QuicDataChannel::Send_n, this, buffer));
+  return worker_thread_->Invoke<bool>(
+      RTC_FROM_HERE, rtc::Bind(&QuicDataChannel::Send_w, this, buffer));
 }
 
-bool QuicDataChannel::Send_n(const DataBuffer& buffer) {
-  RTC_DCHECK(network_thread_->IsCurrent());
+bool QuicDataChannel::Send_w(const DataBuffer& buffer) {
+  RTC_DCHECK(worker_thread_->IsCurrent());
 
   // Encode and send the header containing the data channel ID and message ID.
   rtc::CopyOnWriteBuffer header;
@@ -258,7 +256,7 @@
 }
 
 void QuicDataChannel::OnIncomingMessage(Message&& message) {
-  RTC_DCHECK(network_thread_->IsCurrent());
+  RTC_DCHECK(worker_thread_->IsCurrent());
   RTC_DCHECK(message.stream);
   if (!observer_) {
     LOG(LS_WARNING) << "QUIC data channel " << id_
@@ -297,7 +295,7 @@
 void QuicDataChannel::OnDataReceived(net::QuicStreamId stream_id,
                                      const char* data,
                                      size_t len) {
-  RTC_DCHECK(network_thread_->IsCurrent());
+  RTC_DCHECK(worker_thread_->IsCurrent());
   RTC_DCHECK(data);
   const auto& kv = incoming_quic_messages_.find(stream_id);
   if (kv == incoming_quic_messages_.end()) {
@@ -327,7 +325,7 @@
 }
 
 void QuicDataChannel::OnReadyToSend(cricket::TransportChannel* channel) {
-  RTC_DCHECK(network_thread_->IsCurrent());
+  RTC_DCHECK(worker_thread_->IsCurrent());
   RTC_DCHECK(channel == quic_transport_channel_);
   LOG(LS_INFO) << "QuicTransportChannel is ready to send";
   invoker_.AsyncInvoke<void>(
@@ -344,7 +342,7 @@
 
 void QuicDataChannel::OnIncomingQueuedStreamClosed(net::QuicStreamId stream_id,
                                                    int error) {
-  RTC_DCHECK(network_thread_->IsCurrent());
+  RTC_DCHECK(worker_thread_->IsCurrent());
   LOG(LS_VERBOSE) << "Incoming queued stream " << stream_id << " is closed.";
   incoming_quic_messages_.erase(stream_id);
 }
diff --git a/webrtc/api/quicdatachannel.h b/webrtc/api/quicdatachannel.h
index 18a10ac..a6b987b 100644
--- a/webrtc/api/quicdatachannel.h
+++ b/webrtc/api/quicdatachannel.h
@@ -88,7 +88,6 @@
 
   QuicDataChannel(rtc::Thread* signaling_thread,
                   rtc::Thread* worker_thread,
-                  rtc::Thread* network_thread,
                   const std::string& label,
                   const DataChannelInit& config);
   ~QuicDataChannel() override;
@@ -156,13 +155,11 @@
   void OnReadyToSend(cricket::TransportChannel* channel);
   void OnConnectionClosed();
 
-  // Network thread methods.
+  // Worker thread methods.
   // Sends the data buffer to the remote peer using an outgoing QUIC stream.
   // Returns true if the data buffer can be successfully sent, or if it is
   // queued to be sent later.
-  bool Send_n(const DataBuffer& buffer);
-
-  // Worker thread methods.
+  bool Send_w(const DataBuffer& buffer);
   // Connects the |quic_transport_channel_| signals to this QuicDataChannel,
   // then returns the new QuicDataChannel state.
   DataState SetTransportChannel_w();
@@ -188,10 +185,8 @@
   cricket::QuicTransportChannel* quic_transport_channel_ = nullptr;
   // Signaling thread for DataChannelInterface methods.
   rtc::Thread* const signaling_thread_;
-  // Worker thread for |quic_transport_channel_| callbacks.
+  // Worker thread for sending data and |quic_transport_channel_| callbacks.
   rtc::Thread* const worker_thread_;
-  // Network thread for sending data and |quic_transport_channel_| callbacks.
-  rtc::Thread* const network_thread_;
   rtc::AsyncInvoker invoker_;
   // Map of QUIC stream ID => ReliableQuicStream* for write blocked QUIC
   // streams.
diff --git a/webrtc/api/quicdatachannel_unittest.cc b/webrtc/api/quicdatachannel_unittest.cc
index 7245ccf..e701c29 100644
--- a/webrtc/api/quicdatachannel_unittest.cc
+++ b/webrtc/api/quicdatachannel_unittest.cc
@@ -120,9 +120,8 @@
     DataChannelInit config;
     config.id = id;
     config.protocol = protocol;
-    rtc::scoped_refptr<QuicDataChannel> data_channel(
-        new QuicDataChannel(rtc::Thread::Current(), rtc::Thread::Current(),
-                            rtc::Thread::Current(), label, config));
+    rtc::scoped_refptr<QuicDataChannel> data_channel(new QuicDataChannel(
+        rtc::Thread::Current(), rtc::Thread::Current(), label, config));
     data_channel_by_id_[id] = data_channel;
     return data_channel;
   }
@@ -202,6 +201,8 @@
 
   // Connects |ice_transport_channel_| to that of the other peer.
   void Connect(QuicDataChannelPeer* other_peer) {
+    ice_transport_channel_->Connect();
+    other_peer->ice_transport_channel_->Connect();
     ice_transport_channel_->SetDestination(other_peer->ice_transport_channel_);
   }
 
diff --git a/webrtc/api/quicdatatransport.cc b/webrtc/api/quicdatatransport.cc
index c1caf54..70ad03d 100644
--- a/webrtc/api/quicdatatransport.cc
+++ b/webrtc/api/quicdatatransport.cc
@@ -17,14 +17,10 @@
 namespace webrtc {
 
 QuicDataTransport::QuicDataTransport(rtc::Thread* signaling_thread,
-                                     rtc::Thread* worker_thread,
-                                     rtc::Thread* network_thread)
-    : signaling_thread_(signaling_thread),
-      worker_thread_(worker_thread),
-      network_thread_(network_thread) {
+                                     rtc::Thread* worker_thread)
+    : signaling_thread_(signaling_thread), worker_thread_(worker_thread) {
   RTC_DCHECK(signaling_thread_);
   RTC_DCHECK(worker_thread_);
-  RTC_DCHECK(network_thread_);
 }
 
 QuicDataTransport::~QuicDataTransport() {}
@@ -72,8 +68,8 @@
     LOG(LS_ERROR) << "QUIC data channel already exists with id " << config->id;
     return nullptr;
   }
-  rtc::scoped_refptr<QuicDataChannel> data_channel(new QuicDataChannel(
-      signaling_thread_, worker_thread_, network_thread_, label, *config));
+  rtc::scoped_refptr<QuicDataChannel> data_channel(
+      new QuicDataChannel(signaling_thread_, worker_thread_, label, *config));
   if (quic_transport_channel_) {
     if (!data_channel->SetTransportChannel(quic_transport_channel_)) {
       LOG(LS_ERROR)
diff --git a/webrtc/api/quicdatatransport.h b/webrtc/api/quicdatatransport.h
index 96fe2a0..f0c427d 100644
--- a/webrtc/api/quicdatatransport.h
+++ b/webrtc/api/quicdatatransport.h
@@ -36,9 +36,7 @@
 // exists, it sends the QUIC stream to the QuicDataChannel.
 class QuicDataTransport : public sigslot::has_slots<> {
  public:
-  QuicDataTransport(rtc::Thread* signaling_thread,
-                    rtc::Thread* worker_thread,
-                    rtc::Thread* network_thread);
+  QuicDataTransport(rtc::Thread* signaling_thread, rtc::Thread* worker_thread);
   ~QuicDataTransport() override;
 
   // Sets the QUIC transport channel for the QuicDataChannels and the
@@ -82,10 +80,9 @@
       quic_stream_by_id_;
   // QuicTransportChannel for sending/receiving data.
   cricket::QuicTransportChannel* quic_transport_channel_ = nullptr;
-  // Threads for the QUIC data channel.
+  // Signaling and worker threads for the QUIC data channel.
   rtc::Thread* const signaling_thread_;
   rtc::Thread* const worker_thread_;
-  rtc::Thread* const network_thread_;
 };
 
 }  // namespace webrtc
diff --git a/webrtc/api/quicdatatransport_unittest.cc b/webrtc/api/quicdatatransport_unittest.cc
index 975898e..d668c55 100644
--- a/webrtc/api/quicdatatransport_unittest.cc
+++ b/webrtc/api/quicdatatransport_unittest.cc
@@ -64,9 +64,7 @@
 class QuicDataTransportPeer {
  public:
   QuicDataTransportPeer()
-      : quic_data_transport_(rtc::Thread::Current(),
-                             rtc::Thread::Current(),
-                             rtc::Thread::Current()),
+      : quic_data_transport_(rtc::Thread::Current(), rtc::Thread::Current()),
         ice_transport_channel_(new FakeTransportChannel("data", 0)),
         quic_transport_channel_(ice_transport_channel_) {
     ice_transport_channel_->SetAsync(true);
@@ -82,6 +80,8 @@
 
   // Connects |ice_transport_channel_| to that of the other peer.
   void Connect(QuicDataTransportPeer* other_peer) {
+    ice_transport_channel_->Connect();
+    other_peer->ice_transport_channel_->Connect();
     ice_transport_channel_->SetDestination(other_peer->ice_transport_channel_);
   }