Update platform classes to use OVERRIDE / FINAL when needed

Source/platform/audio/AudioDestination.h

Index: Source/platform/audio/AudioDestination.h
diff --git a/Source/platform/audio/AudioDestination.h b/Source/platform/audio/AudioDestination.h
index 07903ede316c29e4d671de786d1fb1645b02958b..d0566b896c2d0d3b3d4596512cb419c3d55edeed 100644
--- a/Source/platform/audio/AudioDestination.h
+++ b/Source/platform/audio/AudioDestination.h
@@ -61,10 +61,10 @@ public:
     float sampleRate() const { return m_sampleRate; }
 
     // blink::WebAudioDevice::RenderCallback
-    virtual void render(const blink::WebVector<float*>& sourceData, const blink::WebVector<float*>& audioData, size_t numberOfFrames);
+    virtual void render(const blink::WebVector<float*>& sourceData, const blink::WebVector<float*>& audioData, size_t numberOfFrames) OVERRIDE;
 
     // WebCore::AudioSourceProvider
-    virtual void provideInput(AudioBus*, size_t framesToProcess);
+    virtual void provideInput(AudioBus*, size_t framesToProcess) OVERRIDE;
 
     static float hardwareSampleRate();