Refactoring on QUIC related classes.

Merge with the latest webrtc native code.
Remove deprecated function Connect() in QuicTransportChannel.
Fix the compiling issue and broken unit tests by adding the network thread to QUIC related classes.

Review-Url: https://codereview.webrtc.org/2089553002
Cr-Commit-Position: refs/heads/master@{#13472}
diff --git a/webrtc/api/quicdatatransport.h b/webrtc/api/quicdatatransport.h
index f0c427d..96fe2a0 100644
--- a/webrtc/api/quicdatatransport.h
+++ b/webrtc/api/quicdatatransport.h
@@ -36,7 +36,9 @@
 // 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);
+  QuicDataTransport(rtc::Thread* signaling_thread,
+                    rtc::Thread* worker_thread,
+                    rtc::Thread* network_thread);
   ~QuicDataTransport() override;
 
   // Sets the QUIC transport channel for the QuicDataChannels and the
@@ -80,9 +82,10 @@
       quic_stream_by_id_;
   // QuicTransportChannel for sending/receiving data.
   cricket::QuicTransportChannel* quic_transport_channel_ = nullptr;
-  // Signaling and worker threads for the QUIC data channel.
+  // Threads for the QUIC data channel.
   rtc::Thread* const signaling_thread_;
   rtc::Thread* const worker_thread_;
+  rtc::Thread* const network_thread_;
 };
 
 }  // namespace webrtc