Expose codec implementation names in stats.

webrtc/video_receive_stream.h

Index: webrtc/video_receive_stream.h
diff --git a/webrtc/video_receive_stream.h b/webrtc/video_receive_stream.h
index 6be2c5a86eed74628451428454352150565651ec..1cc2477491e44f93a7fa23e6ff98d6585e54bc27 100644
--- a/webrtc/video_receive_stream.h
+++ b/webrtc/video_receive_stream.h
@@ -60,6 +60,7 @@ class VideoReceiveStream : public ReceiveStream {
     int render_frame_rate = 0;
 
     // Decoder stats.
+    std::string decoder_implementation_name = "unknown";
     FrameCounts frame_counts;
     int decode_ms = 0;
     int max_decode_ms = 0;