Add QP stats for sent video streams to StatsReport.

webrtc/video/send_statistics_proxy.cc

Index: webrtc/video/send_statistics_proxy.cc
diff --git a/webrtc/video/send_statistics_proxy.cc b/webrtc/video/send_statistics_proxy.cc
index 551b4b562a43904f6cfe1105d65455b2610126b9..4e3d96752584e7026a691971132e57f9f59a06a2 100644
--- a/webrtc/video/send_statistics_proxy.cc
+++ b/webrtc/video/send_statistics_proxy.cc
@@ -62,6 +62,12 @@ void SendStatisticsProxy::UpdateHistograms() {
   int encode_ms = encode_time_counter_.Avg(kMinRequiredSamples);
   if (encode_ms != -1)
     RTC_HISTOGRAM_COUNTS_1000("WebRTC.Video.EncodeTimeInMs", encode_ms);
+
+  for (const auto& it : qp_counters_) {
+    int qp = it.second.vp8.Avg(kMinRequiredSamples);
+    if (qp != -1)
+      RTC_HISTOGRAM_COUNTS_1000("WebRTC.Video.Vp8.Qp", qp);
+  }
 }
 
 void SendStatisticsProxy::OutgoingRate(const int video_channel,
@@ -162,6 +168,12 @@ void SendStatisticsProxy::OnSendEncodedImage(
   stats->height = encoded_image._encodedHeight;
   update_times_[ssrc].resolution_update_ms = clock_->TimeInMilliseconds();
 
+  if (encoded_image.qp_ != -1 && encoded_image._length > 0) {
+    if (rtp_video_header->codec == kRtpVideoVp8) {
+      qp_counters_[ssrc].vp8.Add(encoded_image.qp_);
+    }
+  }
+
   // TODO(asapersson): This is incorrect if simulcast layers are encoded on
   // different threads and there is no guarantee that one frame of all layers
   // are encoded before the next start.