Expose codec implementation names in stats.

webrtc/modules/video_coding/codecs/vp8/vp8_impl.h

Index: webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
diff --git a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
index 597fb77970879db62e163b469b5d212b1546c8e7..e673ad4e0abea52261bee2217f8cbb35b7d68755 100644
--- a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
+++ b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
@@ -58,6 +58,8 @@ class VP8EncoderImpl : public VP8Encoder {
 
   void OnDroppedFrame() override {}
 
+  const char* ImplementationName() const override;
+
  private:
   void SetupTemporalLayers(int num_streams, int num_temporal_layers,
                            const VideoCodec& codec);
@@ -135,6 +137,8 @@ class VP8DecoderImpl : public VP8Decoder {
   int Release() override;
   int Reset() override;
 
+  const char* ImplementationName() const override;
+
  private:
   // Copy reference image from this _decoder to the _decoder in copyTo. Set
   // which frame type to copy in _refFrame->frame_type before the call to