Implement framesDecoded stat in video receive ssrc stats.

webrtc/api/statscollector.cc

Index: webrtc/api/statscollector.cc
diff --git a/webrtc/api/statscollector.cc b/webrtc/api/statscollector.cc
index aed6b3f4d8b2977c80571d7e01cdd2d33ac6cd5e..417e7a04d68d18f0d4f38a343e6cea8f35e9831e 100644
--- a/webrtc/api/statscollector.cc
+++ b/webrtc/api/statscollector.cc
@@ -228,6 +228,7 @@ void ExtractStats(const cricket::VideoReceiverInfo& info, StatsReport* report) {
     { StatsReport::kStatsValueNamePlisSent, info.plis_sent },
     { StatsReport::kStatsValueNameRenderDelayMs, info.render_delay_ms },
     { StatsReport::kStatsValueNameTargetDelayMs, info.target_delay_ms },
+    { StatsReport::kStatsValueNameFramesDecoded, info.frames_decoded },
   };
 
   for (const auto& i : ints)