Add logging to the QUIC write path.

net/quic/quic_connection.h

Index: net/quic/quic_connection.h
diff --git a/net/quic/quic_connection.h b/net/quic/quic_connection.h
index e7a72a3908071c4e9075a03f08588a005f02605c..fabcc9c8c2bd053f21d17370434c26cd571ff4da 100644
--- a/net/quic/quic_connection.h
+++ b/net/quic/quic_connection.h
@@ -82,10 +82,17 @@ class NET_EXPORT_PRIVATE QuicConnectionVisitorInterface {
 // Interface which gets callbacks from the QuicConnection at interesting
 // points.  Implementations must not mutate the state of the connection
 // as a result of these callbacks.
-class NET_EXPORT_PRIVATE QuicConnectionDebugVisitorInterface {
+class NET_EXPORT_PRIVATE QuicConnectionDebugVisitorInterface
+    : public QuicPacketGenerator::DebugDelegateInterface {
  public:
   virtual ~QuicConnectionDebugVisitorInterface() {}
 
+  // Called when a packet has been sent.
+  virtual void OnPacketSent(QuicPacketSequenceNumber sequence_number,
+                            EncryptionLevel level,
+                            const QuicEncryptedPacket& packet,
+                            int rv) = 0;
+
   // Called when a packet has been received, but before it is
   // validated or parsed.
   virtual void OnPacketReceived(const IPEndPoint& self_address,
@@ -306,6 +313,7 @@ class NET_EXPORT_PRIVATE QuicConnection
   }
   void set_debug_visitor(QuicConnectionDebugVisitorInterface* debug_visitor) {
     debug_visitor_ = debug_visitor;
+    packet_generator_.set_debug_delegate(debug_visitor);
   }
   const IPEndPoint& self_address() const { return self_address_; }
   const IPEndPoint& peer_address() const { return peer_address_; }
@@ -429,6 +437,11 @@ class NET_EXPORT_PRIVATE QuicConnection
                    HasRetransmittableData retransmittable,
                    Force force);
 
+  int WritePacketToWire(QuicPacketSequenceNumber sequence_number,
+                        EncryptionLevel level,
+                        const QuicEncryptedPacket& packet,
+                        int* error);
+
   // Make sure an ack we got from our peer is sane.
   bool ValidateAckFrame(const QuicAckFrame& incoming_ack);