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

Source/modules/mediastream/RTCDataChannelEvent.h

Index: Source/modules/mediastream/RTCDataChannelEvent.h
diff --git a/Source/modules/mediastream/RTCDataChannelEvent.h b/Source/modules/mediastream/RTCDataChannelEvent.h
index 07b72ef82fa23b4c4ebc3fa5b1fedf85dbde7c3a..85dfd854ca75ff7fa9eb181f03e789d336c43b62 100644
--- a/Source/modules/mediastream/RTCDataChannelEvent.h
+++ b/Source/modules/mediastream/RTCDataChannelEvent.h
@@ -34,14 +34,14 @@ namespace blink {
 class RTCDataChannelEvent final : public Event {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    virtual ~RTCDataChannelEvent();
+    ~RTCDataChannelEvent() override;
 
     static PassRefPtrWillBeRawPtr<RTCDataChannelEvent> create();
     static PassRefPtrWillBeRawPtr<RTCDataChannelEvent> create(const AtomicString& type, bool canBubble, bool cancelable, RTCDataChannel*);
 
     RTCDataChannel* channel() const;
 
-    virtual const AtomicString& interfaceName() const override;
+    const AtomicString& interfaceName() const override;
 
     DECLARE_VIRTUAL_TRACE();