Implement framesEncoded stat in video send ssrc stats.

webrtc/video_send_stream.h

Index: webrtc/video_send_stream.h
diff --git a/webrtc/video_send_stream.h b/webrtc/video_send_stream.h
index 43283a55da1e959cd03c098c7e796376f3b9c6ed..c0bee4ed3c9d5cdabea5a28530a43df8d24818c0 100644
--- a/webrtc/video_send_stream.h
+++ b/webrtc/video_send_stream.h
@@ -56,6 +56,7 @@ class VideoSendStream {
     int encode_frame_rate = 0;
     int avg_encode_time_ms = 0;
     int encode_usage_percent = 0;
+    uint32_t frames_encoded = 0;
     // Bitrate the encoder is currently configured to use due to bandwidth
     // limitations.
     int target_media_bitrate_bps = 0;