Add separate send-side UMA stats for screenshare and video.

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 7209094fe68a70342de60992ea2acc6e4528ef47..299340af034e63d3a3f46d3ecfd6b9d94cb9b99b 100644
--- a/webrtc/video/send_statistics_proxy.h
+++ b/webrtc/video/send_statistics_proxy.h
@@ -38,7 +38,9 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
  public:
   static const int kStatsTimeoutMs;
 
-  SendStatisticsProxy(Clock* clock, const VideoSendStream::Config& config);
+  SendStatisticsProxy(Clock* clock,
+                      const VideoSendStream::Config& config,
+                      const VideoEncoderConfig& encoder_config);
   virtual ~SendStatisticsProxy();
 
   VideoSendStream::Stats GetStats();
@@ -112,19 +114,21 @@ class SendStatisticsProxy : public CpuOveruseMetricsObserver,
     int num_samples;
   };
   struct StatsUpdateTimes {
-    StatsUpdateTimes() : resolution_update_ms(0) {}
+    StatsUpdateTimes() : resolution_update_ms(0), bitrate_update_ms(0) {}
     int64_t resolution_update_ms;
     int64_t bitrate_update_ms;
   };
   void PurgeOldStats() EXCLUSIVE_LOCKS_REQUIRED(crit_);
   VideoSendStream::StreamStats* GetStatsEntry(uint32_t ssrc)
       EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
   void UpdateHistograms() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   Clock* const clock_;
   const VideoSendStream::Config config_;
   mutable rtc::CriticalSection crit_;
   VideoSendStream::Stats stats_ GUARDED_BY(crit_);
+  const std::string uma_prefix_;
   rtc::RateTracker input_frame_rate_tracker_ GUARDED_BY(crit_);
   rtc::RateTracker sent_frame_rate_tracker_ GUARDED_BY(crit_);
   uint32_t last_sent_frame_timestamp_ GUARDED_BY(crit_);