Implement qpSum stat for video send ssrc stats.

webrtc/media/base/mediachannel.h

Index: webrtc/media/base/mediachannel.h
diff --git a/webrtc/media/base/mediachannel.h b/webrtc/media/base/mediachannel.h
index a72b553aa1d3c57cd8a047e5c6e362d7b6d37731..538d5f543fbf4de96db5db29d219c5869a5ccadd 100644
--- a/webrtc/media/base/mediachannel.h
+++ b/webrtc/media/base/mediachannel.h
@@ -666,7 +666,8 @@ struct VideoSenderInfo : public MediaSenderInfo {
         adapt_changes(0),
         avg_encode_ms(0),
         encode_usage_percent(0),
-        frames_encoded(0) {}
+        frames_encoded(0),
+        qp_sum(0) {}
 
   std::vector<SsrcGroup> ssrc_groups;
   std::string encoder_implementation_name;
@@ -685,6 +686,7 @@ struct VideoSenderInfo : public MediaSenderInfo {
   int avg_encode_ms;
   int encode_usage_percent;
   int frames_encoded;
+  int qp_sum;

[hbos, 2016/10/20 17:08:21]

Should be uint32_t.

What about the decoded case? I think there should be a qp_sum in
VideoReceiverInfo as well.

From spec:
  The sum of the QP values of frames passed. The count
  of frames is in framesDecoded for inbound
  stream stats, and in framesEncoded for
  outbound stream stats.

This only covers the RTCOutboundRTPStreamStats case.

[sakal, 2016/10/21 08:59:43]

I'd prefer to implement it in another CL. It will be considerably more work and
adding this for the encoding case satisfies our immediate use case.

 };
 
 struct VideoReceiverInfo : public MediaReceiverInfo {