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/quicdatachannel.h b/webrtc/api/quicdatachannel.h
index a6b987b..18a10ac 100644
--- a/webrtc/api/quicdatachannel.h
+++ b/webrtc/api/quicdatachannel.h
@@ -88,6 +88,7 @@
 
   QuicDataChannel(rtc::Thread* signaling_thread,
                   rtc::Thread* worker_thread,
+                  rtc::Thread* network_thread,
                   const std::string& label,
                   const DataChannelInit& config);
   ~QuicDataChannel() override;
@@ -155,11 +156,13 @@
   void OnReadyToSend(cricket::TransportChannel* channel);
   void OnConnectionClosed();
 
-  // Worker thread methods.
+  // Network 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_w(const DataBuffer& buffer);
+  bool Send_n(const DataBuffer& buffer);
+
+  // Worker thread methods.
   // Connects the |quic_transport_channel_| signals to this QuicDataChannel,
   // then returns the new QuicDataChannel state.
   DataState SetTransportChannel_w();
@@ -185,8 +188,10 @@
   cricket::QuicTransportChannel* quic_transport_channel_ = nullptr;
   // Signaling thread for DataChannelInterface methods.
   rtc::Thread* const signaling_thread_;
-  // Worker thread for sending data and |quic_transport_channel_| callbacks.
+  // Worker thread for |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.