Adding missing stats class registration, lost in #10298.

webrtc/video/video_send_stream.cc

Index: webrtc/video/video_send_stream.cc
diff --git a/webrtc/video/video_send_stream.cc b/webrtc/video/video_send_stream.cc
index b7b0150e8e6004487258edf73ac2ee25ae6a06f1..3adb2f774ca953069ff0899096709749aba4e971 100644
--- a/webrtc/video/video_send_stream.cc
+++ b/webrtc/video/video_send_stream.cc
@@ -154,6 +154,9 @@ VideoSendStream::VideoSendStream(
       channel_group_->packet_router(), ssrcs.size(), true));
   RTC_CHECK(vie_channel_->Init() == 0);
 
+  channel_group_->GetCallStats()->RegisterStatsObserver(
+      vie_channel_->GetStatsObserver());
+
   vie_encoder_->StartThreadsAndSetSharedMembers(
       vie_channel_->send_payload_router(),
       vie_channel_->vcm_protection_callback());