Fix virtual/override/final usage in Source/platform/.

Source/platform/mediastream/MediaStreamComponent.h

Index: Source/platform/mediastream/MediaStreamComponent.h
diff --git a/Source/platform/mediastream/MediaStreamComponent.h b/Source/platform/mediastream/MediaStreamComponent.h
index 866ce4985c05ada67d0ec4c729d87805f62923b3..08809488c4ae3a8cada2806b765ac76b62db50d5 100644
--- a/Source/platform/mediastream/MediaStreamComponent.h
+++ b/Source/platform/mediastream/MediaStreamComponent.h
@@ -84,13 +84,13 @@ private:
         {
         }
 
-        virtual ~AudioSourceProviderImpl() { }
+        ~AudioSourceProviderImpl() override {}
 
         // Wraps the given blink::WebAudioSourceProvider to blink::AudioSourceProvider.
         void wrap(WebAudioSourceProvider*);
 
         // blink::AudioSourceProvider
-        virtual void provideInput(AudioBus*, size_t framesToProcess) override;
+        void provideInput(AudioBus*, size_t framesToProcess) override;
 
     private:
         WebAudioSourceProvider* m_webAudioSourceProvider;