Expose codec implementation names in stats.

webrtc/test/fake_encoder.h

Index: webrtc/test/fake_encoder.h
diff --git a/webrtc/test/fake_encoder.h b/webrtc/test/fake_encoder.h
index 88ff9d40f30bb52b940c26f6201c293489bf0959..6bff00e2a314fd0ca1310f83c5094a93fb266258 100644
--- a/webrtc/test/fake_encoder.h
+++ b/webrtc/test/fake_encoder.h
@@ -39,6 +39,9 @@ class FakeEncoder : public VideoEncoder {
   int32_t Release() override;
   int32_t SetChannelParameters(uint32_t packet_loss, int64_t rtt) override;
   int32_t SetRates(uint32_t new_target_bitrate, uint32_t framerate) override;
+  const char* ImplementationName() const override;
+
+  static const char* kImplementationName;
 
  protected:
   Clock* const clock_;