Adding missing stats class registration, lost in #10298.

R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1408233004 .

Cr-Commit-Position: refs/heads/master@{#10334}

webrtc/video/video_receive_stream.cc

@@ -169,7 +169,6 @@ VideoReceiveStream::VideoReceiveStream(int num_cpu_cores,
   channel_group_->GetCallStats()->RegisterStatsObserver(
       vie_channel_->GetStatsObserver());
 
-
   // TODO(pbos): This is not fine grained enough...
   vie_channel_->SetProtectionMode(config_.rtp.nack.rtp_history_ms > 0, false,
                                   -1, -1);

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());