Add stats for average QP per frame for VP8 (for received video streams).

webrtc/video/receive_statistics_proxy.h

Index: webrtc/video/receive_statistics_proxy.h
diff --git a/webrtc/video/receive_statistics_proxy.h b/webrtc/video/receive_statistics_proxy.h
index 6e4fd3a618ec5861a2afbec066543d64eccaf05f..b6741f9cde163b7105462997d130436abc6db452 100644
--- a/webrtc/video/receive_statistics_proxy.h
+++ b/webrtc/video/receive_statistics_proxy.h
@@ -30,6 +30,7 @@ namespace webrtc {
 class Clock;
 class ViECodec;
 class ViEDecoderObserver;
+struct CodecSpecificInfo;
 
 class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
                                public RtcpStatisticsCallback,
@@ -54,6 +55,9 @@ class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
                        int render_delay_ms,
                        int64_t rtt_ms);
 
+  void OnPreDecode(const EncodedImage& encoded_image,
+                   const CodecSpecificInfo* codec_specific_info);
+
   // Overrides VCMReceiveStatisticsCallback.
   void OnReceiveRatesUpdated(uint32_t bitRate, uint32_t frameRate) override;
   void OnFrameCountsUpdated(const FrameCounts& frame_counts) override;
@@ -82,6 +86,9 @@ class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
     int sum;
     int num_samples;
   };
+  struct QpCounters {
+    SampleCounter vp8;
+  };
 
   void UpdateHistograms() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
@@ -98,6 +105,7 @@ class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
   SampleCounter decode_time_counter_ GUARDED_BY(crit_);
   SampleCounter delay_counter_ GUARDED_BY(crit_);
   ReportBlockStats report_block_stats_ GUARDED_BY(crit_);
+  QpCounters qp_counters_;  // Only accessed on the decoding thread.
 };
 
 }  // namespace webrtc