Start using the loss timeout in QuicSentPacketManager and add a mock

net/quic/congestion_control/loss_detection_interface.h

Index: net/quic/congestion_control/loss_detection_interface.h
diff --git a/net/quic/congestion_control/loss_detection_interface.h b/net/quic/congestion_control/loss_detection_interface.h
index 85d51e3fa1f224f2760718de7495af056e232861..f9ec428e10f2d050fadf20b4d135009ad4dcb5ee 100644
--- a/net/quic/congestion_control/loss_detection_interface.h
+++ b/net/quic/congestion_control/loss_detection_interface.h
@@ -28,6 +28,10 @@ class NET_EXPORT_PRIVATE LossDetectionInterface {
       const QuicTime& time,
       QuicPacketSequenceNumber largest_observed,
       QuicTime::Delta srtt) = 0;
+
+  // Get the time the LossDetectionAlgorithm wants to re-evaluate losses.
+  // Returns QuicTime::Zero if no alarm needs to be set.
+  virtual QuicTime GetLossTimeout() const = 0;
 };
 
 }  // namespace net