Notify NQE of TCP RTT values

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..b31d3b4ba7852e984f006e1e39c1892791775936 100644
--- a/net/base/socket_performance_watcher.h
+++ b/net/base/socket_performance_watcher.h
@@ -6,6 +6,7 @@
 #define NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 
 #include "base/macros.h"
+#include "base/time/time.h"
 #include "net/base/net_export.h"
 #include "net/base/socket_performance_watcher_factory.h"
 
@@ -33,10 +34,26 @@ class NET_EXPORT_PRIVATE SocketPerformanceWatcher {
   // made, hence no timestamp.
   void OnUpdatedRTTAvailable(const base::TimeDelta& rtt) const;
 
+  base::TimeDelta rtt_notification_interval() const {
+    // TODO(tbansal): TCP/QUIC start with a hard-coded RTT estimate, and
+    // converge to a more accurate value as more packets are received. This
+    // function should be changed to return 0 seconds until this connection
+    // has received 15 packets. Afterwards, it should return 2 seconds.

[Ryan Sleevi, 2016/02/25 22:48:46]

Why not return this as a "const base::TimeDelta&" ?

Also, this comment seems like it belongs in a crbug.com, not here.

[tbansal1, 2016/02/26 23:43:34]

I think mmenke said at one point that it is okay to return TimeDelta by value,
because that class only contains an int64 member. I can't find that comment in
the review history, so I may be wrong. Also, codesearch shows it not returned by
reference 2200 times
(https://code.google.com/p/chromium/codesearch#search/&q=TimeDelta%5C%20%5BA-Z...),
and by reference 500 times
(https://code.google.com/p/chromium/codesearch#search/&q=TimeDelta&%5C%20%...).
I was going to fix that in the next CL but filed a new bug (crbug.com/590300).

+    return rtt_notification_interval_;
+  }
+
+  // Called when |this| socket performance watcher is reused for establishing a
+  // new transport layer connection.
+  void Reset() const;
+
  private:
   // Transport layer protocol used by the socket that |this| is watching.
   const SocketPerformanceWatcherFactory::Protocol protocol_;
 
+  // Minimum time interval between two successive OnUpdatedRTTAvailable
+  // notifications to |this|.
+  const base::TimeDelta rtt_notification_interval_;
+
   // |socket_performance_watcher_factory_| is the factory that created
   // |this| watcher.
   SocketPerformanceWatcherFactory* socket_performance_watcher_factory_;