Expose codec implementation names in stats.

webrtc/modules/video_coding/main/source/generic_encoder.h

Index: webrtc/modules/video_coding/main/source/generic_encoder.h
diff --git a/webrtc/modules/video_coding/main/source/generic_encoder.h b/webrtc/modules/video_coding/main/source/generic_encoder.h
index 25235b6b4677ad2565a9d6583bc2cf565727cd40..be49ea5fd04139aba32b1815ad7656233c067ecb 100644
--- a/webrtc/modules/video_coding/main/source/generic_encoder.h
+++ b/webrtc/modules/video_coding/main/source/generic_encoder.h
@@ -55,6 +55,7 @@ public:
     void SetInternalSource(bool internalSource) { _internalSource = internalSource; };
 
     void SetRotation(VideoRotation rotation) { _rotation = rotation; }
+    void LastEncoderImplementationUsed(const char* encoder_implementation_name);
 
 private:
     VCMPacketizationCallback* _sendCallback;
@@ -145,11 +146,11 @@ public:
 private:
     VideoEncoder* const encoder_;
     VideoEncoderRateObserver* const rate_observer_;
-    VCMEncodedFrameCallback*  vcm_encoded_frame_callback_;
-    uint32_t bit_rate_;
-    uint32_t frame_rate_;
-    const bool internal_source_;
+    VCMEncodedFrameCallback* vcm_encoded_frame_callback_;
     mutable rtc::CriticalSection rates_lock_;
+    uint32_t bit_rate_ GUARDED_BY(rates_lock_);
+    uint32_t frame_rate_ GUARDED_BY(rates_lock_);
+    const bool internal_source_;
     VideoRotation rotation_;
     bool is_screenshare_;
 }; // end of VCMGenericEncoder class