Expose packet loss counts from QUIC to NetworkQualityEstimator

net/base/socket_performance_watcher.h

Index: net/base/socket_performance_watcher.h
diff --git a/net/base/socket_performance_watcher.h b/net/base/socket_performance_watcher.h
index e0e76327ce63541e8d0dc2ba23215d34f953df41..6594970a8a21a008b67838f14296d8dd575e7358 100644
--- a/net/base/socket_performance_watcher.h
+++ b/net/base/socket_performance_watcher.h
@@ -5,6 +5,9 @@
 #ifndef NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 #define NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 
+#include <stddef.h>
+#include <stdint.h>
+
 #include "base/macros.h"
 #include "net/base/net_export.h"
 #include "net/base/socket_performance_watcher_factory.h"
@@ -33,6 +36,22 @@ class NET_EXPORT_PRIVATE SocketPerformanceWatcher {
   // made, hence no timestamp.
   void OnUpdatedRTTAvailable(const base::TimeDelta& rtt) const;
 
+  // Called when an updated packet count at the transport layer is available.
+  // All the counts are since the last call to the
+  // OnUpdatedPacketCountAvailable. This method is called immediately after the
+  // observation is made, hence no timestamp.
+
+  // An example:
+  // Last observation after packet #1. Packets #5 and #6 are received:
+  //   missing = 3, in_order = 2, out_of_order = 0.
+
+  // Last observation after packet #6. Packet #3 received:
+  //   missing = 0, in_order = 0, out_of_order = 1.
+  void OnUpdatedPacketCountAvailable(

[Ryan Hamilton, 2016/03/07 20:02:10]

Perhaps s/Updated/Incremental/?

[tbansal1, 2016/03/08 02:59:58]

Done.

+      size_t packets_missing,

[Ryan Hamilton, 2016/03/07 20:02:10]

I was hoping to see a comment here about how out_of_order and missing interact
to determine the packet loss rate. Can you add one?

[tbansal1, 2016/03/08 02:59:58]

There are  2 use cases for this: (1) Report the raw incremental packet count
numbers to the observers (One app based on Cronet is waiting for this CL. They
plan to run their own logic on the raw data).
(2) Compute the packet loss rate for use within Chromium. This would require
figuring out how the 3 counts interact with each other. I added some more
comments in nqe.cc::OnIncrementalPacketCountAvailable() on how this can be done.
I have removed the code for this from this CL since at this point, it is not
clear if it is really needed.

+      size_t packets_received_in_order,
+      size_t packets_received_out_of_order) const;
+
  private:
   // Transport layer protocol used by the socket that |this| is watching.
   const SocketPerformanceWatcherFactory::Protocol protocol_;