Add histogram stats for send delay for a sent video stream.

webrtc/video/send_statistics_proxy.h

Index: webrtc/video/send_statistics_proxy.h
diff --git a/webrtc/video/send_statistics_proxy.h b/webrtc/video/send_statistics_proxy.h
index bb0372aec18542597c73bd49d87f78fb3277b1b2..c99b6b17949f436d141eb99facaf04b104c0033c 100644
--- a/webrtc/video/send_statistics_proxy.h
+++ b/webrtc/video/send_statistics_proxy.h
@@ -37,7 +37,8 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
                             public BitrateStatisticsObserver,
                             public FrameCountObserver,
                             public VideoEncoderRateObserver,
-                            public SendSideDelayObserver {
+                            public SendSideDelayObserver,
+                            public SendPacketObserver {
  public:
   static const int kStatsTimeoutMs;
 
@@ -69,6 +70,9 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
   void OnEncodedFrameTimeMeasured(int encode_time_ms,
                                   const CpuOveruseMetrics& metrics) override;
 
+  // Called when a packet is sent (leaving socket).
+  bool OnSentPacket(int packet_id);
+
  protected:
   // From RtcpStatisticsCallback.
   void StatisticsUpdated(const RtcpStatistics& statistics,
@@ -95,7 +99,30 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
                             int max_delay_ms,
                             uint32_t ssrc) override;
 
+  // From SendPacketObserver.
+  // Called when a packet is sent to the transport.
+  void OnSendPacket(uint16_t packet_id,
+                    int64_t capture_time_ms,
+                    uint32_t ssrc) override;
+
  private:
+  // Map holding sent packets (mapped by sequence number).
+  struct SequenceNumberOlderThan {
+    bool operator()(uint16_t seq1, uint16_t seq2) const {
+      return IsNewerSequenceNumber(seq2, seq1);
+    }
+  };
+  struct Packet {
+    Packet(uint32_t ssrc, int64_t capture_time_ms, int64_t send_time_ms)
+        : ssrc(ssrc),
+          capture_time_ms(capture_time_ms),
+          send_time_ms(send_time_ms) {}
+    uint32_t ssrc;
+    int64_t capture_time_ms;
+    int64_t send_time_ms;
+  };
+  typedef std::map<uint16_t, Packet, SequenceNumberOlderThan> PacketMap;
+
   class SampleCounter {
    public:
     SampleCounter() : sum(0), num_samples(0) {}
@@ -132,6 +159,8 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
   void PurgeOldStats() EXCLUSIVE_LOCKS_REQUIRED(crit_);
   VideoSendStream::StreamStats* GetStatsEntry(uint32_t ssrc)
       EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  void RemoveOld(int64_t now, PacketMap* packets)
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   Clock* const clock_;
   const VideoSendStream::Config config_;
@@ -142,6 +171,11 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
   std::map<uint32_t, StatsUpdateTimes> update_times_ GUARDED_BY(crit_);
   rtc::ExpFilter encode_time_ GUARDED_BY(crit_);
 
+  // Send delay stats.
+  PacketMap packets_ GUARDED_BY(crit_);
+  size_t num_old_packets_;
+  size_t num_skipped_packets_;
+
   // Contains stats used for UMA histograms. These stats will be reset if
   // content type changes between real-time video and screenshare, since these
   // will be reported separately.
@@ -178,6 +212,7 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
     const VideoSendStream::Stats start_stats_;
     std::map<int, QpCounters>
         qp_counters_;  // QP counters mapped by spatial idx.
+    std::map<uint32_t, SampleCounter> send_delay_counters_;  // Mapped by SSRC.
   };
 
   std::unique_ptr<UmaSamplesContainer> uma_container_ GUARDED_BY(crit_);