Add QP stats for received video streams to StatsReport.

webrtc/video/receive_statistics_proxy.cc

Index: webrtc/video/receive_statistics_proxy.cc
diff --git a/webrtc/video/receive_statistics_proxy.cc b/webrtc/video/receive_statistics_proxy.cc
index 5b456a817f5511f939db3a2dbd608b5020118ec4..bd00edc4bed66d141c08bca1719ee39151730277 100644
--- a/webrtc/video/receive_statistics_proxy.cc
+++ b/webrtc/video/receive_statistics_proxy.cc
@@ -19,6 +19,9 @@
 #include "webrtc/system_wrappers/interface/metrics.h"
 
 namespace webrtc {
+namespace {
+const float kQpWeigthFactor = 0.97f;
+}  // namespace
 
 ReceiveStatisticsProxy::ReceiveStatisticsProxy(uint32_t ssrc, Clock* clock)
     : clock_(clock),
@@ -26,7 +29,8 @@ ReceiveStatisticsProxy::ReceiveStatisticsProxy(uint32_t ssrc, Clock* clock)
       decode_fps_estimator_(1000, 1000),
       renders_fps_estimator_(1000, 1000),
       render_fps_tracker_(100u, 10u),
-      render_pixel_tracker_(100u, 10u) {
+      render_pixel_tracker_(100u, 10u),
+      qp_(kQpWeigthFactor) {
   stats_.ssrc = ssrc;
 }
 
@@ -194,6 +198,10 @@ void ReceiveStatisticsProxy::OnPreDecode(
   if (codec_specific_info->codecType == kVideoCodecVP8) {
     qp_counters_.vp8.Add(encoded_image.qp_);
   }
+  qp_.Apply(1.0f, encoded_image.qp_);
+
+  rtc::CritScope lock(&crit_);
+  stats_.qp = round(qp_.filtered());
 }
 
 void ReceiveStatisticsProxy::SampleCounter::Add(int sample) {