Add UMA to net::BidirectionalStream

net/http/bidirectional_stream.h

Index: net/http/bidirectional_stream.h
diff --git a/net/http/bidirectional_stream.h b/net/http/bidirectional_stream.h
index 0b86870ba44e3e4808f2670c9409585d8a382873..c7fa97cdf687a731c33090a840f345df3cc68cdc 100644
--- a/net/http/bidirectional_stream.h
+++ b/net/http/bidirectional_stream.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
 #include "net/http/bidirectional_stream_impl.h"
 #include "net/http/http_stream_factory.h"
 #include "net/log/net_log.h"
@@ -213,6 +214,8 @@ class NET_EXPORT BidirectionalStream
   // Helper method to notify delegate if there is an error.
   void NotifyFailed(int error);
 
+  void UpdateHistograms();
+
   // BidirectionalStreamRequestInfo used when requesting the stream.
   std::unique_ptr<BidirectionalStreamRequestInfo> request_info_;
   const BoundNetLog net_log_;
@@ -243,6 +246,12 @@ class NET_EXPORT BidirectionalStream
   // List of buffer length.
   std::vector<int> write_buffer_len_list_;
 
+  base::TimeTicks start_time_;

[mef, 2016/08/11 15:42:19]

Would it make sense to replace individual timeticks with net::LoadTimingInfo
here? Some of the fields will be unused, but it could make it easier to use for
Metrics API implementation.

[xunjieli, 2016/08/11 19:37:09]

That's a great idea! How about doing this as a follow-up? I'd like to add
support for LoadTimingInfo in QUIC as well. I can refactor this once that is
ready. What do you think?

LoadTimingInfo doesn't have a counter part for |read_end_time_|, so that's
something we need to investigate as well for the metrics API.

[mef, 2016/08/12 15:44:45]

sgtm. Interesting observation about missing read_end_time_, I didn't realize
that. 

+  base::TimeTicks read_start_time_;
+  base::TimeTicks read_end_time_;
+  base::TimeTicks send_start_time_;
+  base::TimeTicks send_end_time_;
+
   base::WeakPtrFactory<BidirectionalStream> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BidirectionalStream);