Update platform classes to use OVERRIDE / FINAL when needed

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 dde28ce65e8269c30b3cba4580969ff067feb186..b084347672a6724531862c4b4782b73aece04a93 100644
--- a/Source/platform/mediastream/MediaStreamComponent.h
+++ b/Source/platform/mediastream/MediaStreamComponent.h
@@ -82,7 +82,7 @@ private:
     // AudioSourceProviderImpl wraps a WebAudioSourceProvider::provideInput()
     // calls into chromium to get a rendered audio stream.
 
-    class AudioSourceProviderImpl : public AudioSourceProvider {
+    class AudioSourceProviderImpl FINAL: public AudioSourceProvider {
     public:
         AudioSourceProviderImpl()
             : m_webAudioSourceProvider(0)
@@ -95,7 +95,7 @@ private:
         void wrap(blink::WebAudioSourceProvider*);
 
         // WebCore::AudioSourceProvider
-        virtual void provideInput(WebCore::AudioBus*, size_t framesToProcess);
+        virtual void provideInput(WebCore::AudioBus*, size_t framesToProcess) OVERRIDE;
 
     private:
         blink::WebAudioSourceProvider* m_webAudioSourceProvider;