Add histogram stats for number of cpu/quality adapt changes per minute for sent video streams:

webrtc/video/send_statistics_proxy.h

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 41 matching lines @@
 
   virtual VideoSendStream::Stats GetStats();
 
   virtual void OnSendEncodedImage(const EncodedImage& encoded_image,
                                   const CodecSpecificInfo* codec_info);
   // Used to update incoming frame rate.
   void OnIncomingFrame(int width, int height);
 
   void OnCpuRestrictedResolutionChanged(bool cpu_restricted_resolution);
   void OnQualityRestrictedResolutionChanged(int num_quality_downscales);
-  void SetCpuScalingStats(bool cpu_restricted_resolution);
+  void SetCpuScalingStats(int num_cpu_downscales);  // -1: disabled.
   void SetQualityScalingStats(int num_quality_downscales);  // -1: disabled.
 
   void OnEncoderStatsUpdate(uint32_t framerate, uint32_t bitrate);
   void OnSuspendChange(bool is_suspended);
   void OnInactiveSsrc(uint32_t ssrc);
 
   // Used to indicate change in content type, which may require a change in
   // how stats are collected and set the configured preferred media bitrate.
   void OnEncoderReconfigured(const VideoEncoderConfig& encoder_config,
                              uint32_t preferred_bitrate_bps);
@@ skipping 64 matching lines @@
     int64_t resolution_update_ms;
     int64_t bitrate_update_ms;
   };
   struct TargetRateUpdates {
     TargetRateUpdates()
         : pause_resume_events(0), last_paused_or_resumed(false), last_ms(-1) {}
     int pause_resume_events;
     bool last_paused_or_resumed;
     int64_t last_ms;
   };
+  struct StatsTimer {
+    void Start(int64_t now_ms);
+    void Stop(int64_t now_ms);
+    void Restart(int64_t now_ms);
+    int64_t start_ms = -1;
+    int64_t total_ms = 0;
+  };
   struct QpCounters {
-    SampleCounter vp8;   // QP range: 0-127
-    SampleCounter vp9;   // QP range: 0-255
-    SampleCounter h264;  // QP range: 0-51
+    SampleCounter vp8;   // QP range: 0-127.
+    SampleCounter vp9;   // QP range: 0-255.
+    SampleCounter h264;  // QP range: 0-51.
   };
   void PurgeOldStats() EXCLUSIVE_LOCKS_REQUIRED(crit_);
   VideoSendStream::StreamStats* GetStatsEntry(uint32_t ssrc)
       EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   Clock* const clock_;
   const std::string payload_name_;
   const VideoSendStream::Config::Rtp rtp_config_;
   rtc::CriticalSection crit_;
   VideoEncoderConfig::ContentType content_type_ GUARDED_BY(crit_);
@@ skipping 39 matching lines @@
     RateCounter input_fps_counter_;
     RateCounter sent_fps_counter_;
     RateAccCounter total_byte_counter_;
     RateAccCounter media_byte_counter_;
     RateAccCounter rtx_byte_counter_;
     RateAccCounter padding_byte_counter_;
     RateAccCounter retransmit_byte_counter_;
     RateAccCounter fec_byte_counter_;
     int64_t first_rtcp_stats_time_ms_;
     int64_t first_rtp_stats_time_ms_;
+    StatsTimer cpu_scaling_timer_;
+    StatsTimer quality_scaling_timer_;
     BoolSampleCounter paused_time_counter_;
     TargetRateUpdates target_rate_updates_;
     ReportBlockStats report_block_stats_;
     const VideoSendStream::Stats start_stats_;
 
     std::map<int, QpCounters>
         qp_counters_;  // QP counters mapped by spatial idx.
   };
 
   std::unique_ptr<UmaSamplesContainer> uma_container_ GUARDED_BY(crit_);
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_VIDEO_SEND_STATISTICS_PROXY_H_