Standardize usage of virtual/override/final in media/

media/cast/receiver/video_decoder.cc

Index: media/cast/receiver/video_decoder.cc
diff --git a/media/cast/receiver/video_decoder.cc b/media/cast/receiver/video_decoder.cc
index 1eaa6f346e0cccc90f839eb82502e487a85819d2..e536c3e23b52f2f3b7ac5edcc011b9202e43f155 100644
--- a/media/cast/receiver/video_decoder.cc
+++ b/media/cast/receiver/video_decoder.cc
@@ -114,12 +114,12 @@ class VideoDecoder::Vp8Impl : public VideoDecoder::ImplBase {
   }
 
  private:
-  virtual ~Vp8Impl() {
+  ~Vp8Impl() override {
     if (ImplBase::cast_initialization_status_ == STATUS_VIDEO_INITIALIZED)
       CHECK_EQ(VPX_CODEC_OK, vpx_codec_destroy(&context_));
   }
 
-  virtual scoped_refptr<VideoFrame> Decode(uint8* data, int len) override {
+  scoped_refptr<VideoFrame> Decode(uint8* data, int len) override {
     if (len <= 0 || vpx_codec_decode(&context_,
                                      data,
                                      static_cast<unsigned int>(len),
@@ -181,9 +181,9 @@ class VideoDecoder::FakeImpl : public VideoDecoder::ImplBase {
   }
 
  private:
-  virtual ~FakeImpl() {}
+  ~FakeImpl() override {}
 
-  virtual scoped_refptr<VideoFrame> Decode(uint8* data, int len) override {
+  scoped_refptr<VideoFrame> Decode(uint8* data, int len) override {
     // Make sure this is a JSON string.
     if (!len || data[0] != '{')
       return NULL;