Standardize usage of virtual/override/final specifiers in content/.

content/renderer/media/webrtc/video_destination_handler.cc

Index: content/renderer/media/webrtc/video_destination_handler.cc
diff --git a/content/renderer/media/webrtc/video_destination_handler.cc b/content/renderer/media/webrtc/video_destination_handler.cc
index 4f7664584dcd80ce1c9bce40a713bc09b32bc646..75e62d0c498b36d3ca4d8c0feb1bf3bea38e6710 100644
--- a/content/renderer/media/webrtc/video_destination_handler.cc
+++ b/content/renderer/media/webrtc/video_destination_handler.cc
@@ -189,10 +189,9 @@ class PpFrameWriterProxy : public FrameWriterInterface {
     DCHECK(writer_ != NULL);
   }
 
-  virtual ~PpFrameWriterProxy() {}
+  ~PpFrameWriterProxy() override {}
 
-  virtual void PutFrame(PPB_ImageData_Impl* image_data,
-                        int64 time_stamp_ns) override {
+  void PutFrame(PPB_ImageData_Impl* image_data, int64 time_stamp_ns) override {
     writer_->PutFrame(image_data, time_stamp_ns);
   }