Enable -Winconsistent-missing-override flag.

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 6906a322afcf7ffb45200611c02844167e489037..f8af642253824c8bb96a72c17d3e91ef1ea6b294 100644
--- a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
+++ b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
@@ -40,21 +40,21 @@ class VP8EncoderImpl : public VP8Encoder {
 
   virtual ~VP8EncoderImpl();
 
-  virtual int Release();
+  int Release() override;
 
-  virtual int InitEncode(const VideoCodec* codec_settings,
-                         int number_of_cores,
-                         size_t max_payload_size);
+  int InitEncode(const VideoCodec* codec_settings,
+                 int number_of_cores,
+                 size_t max_payload_size) override;
 
-  virtual int Encode(const VideoFrame& input_image,
-                     const CodecSpecificInfo* codec_specific_info,
-                     const std::vector<FrameType>* frame_types);
+  int Encode(const VideoFrame& input_image,
+             const CodecSpecificInfo* codec_specific_info,
+             const std::vector<FrameType>* frame_types) override;
 
-  virtual int RegisterEncodeCompleteCallback(EncodedImageCallback* callback);
+  int RegisterEncodeCompleteCallback(EncodedImageCallback* callback) override;
 
-  virtual int SetChannelParameters(uint32_t packet_loss, int64_t rtt);
+  int SetChannelParameters(uint32_t packet_loss, int64_t rtt) override;
 
-  virtual int SetRates(uint32_t new_bitrate_kbit, uint32_t frame_rate);
+  int SetRates(uint32_t new_bitrate_kbit, uint32_t frame_rate) override;
 
   void OnDroppedFrame() override {}