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

Source/modules/mediastream/RTCDataChannel.h

Index: Source/modules/mediastream/RTCDataChannel.h
diff --git a/Source/modules/mediastream/RTCDataChannel.h b/Source/modules/mediastream/RTCDataChannel.h
index e644878039618a6c3c3d0667fce7f6d24984720b..f26aed0e530ecc4e7935f57429b8319bb4f05dd0 100644
--- a/Source/modules/mediastream/RTCDataChannel.h
+++ b/Source/modules/mediastream/RTCDataChannel.h
@@ -50,7 +50,7 @@ class RTCDataChannel final
 public:
     static RTCDataChannel* create(ExecutionContext*, RTCPeerConnection*, PassOwnPtr<WebRTCDataChannelHandler>);
     static RTCDataChannel* create(ExecutionContext*, RTCPeerConnection*, WebRTCPeerConnectionHandler*, const String& label, const WebRTCDataChannelInit&, ExceptionState&);
-    virtual ~RTCDataChannel();
+    ~RTCDataChannel() override;
 
     ReadyState getHandlerState() const;
 
@@ -86,8 +86,8 @@ public:
     void stop();
 
     // EventTarget
-    virtual const AtomicString& interfaceName() const override;
-    virtual ExecutionContext* executionContext() const override;
+    const AtomicString& interfaceName() const override;
+    ExecutionContext* executionContext() const override;
 
     void clearWeakMembers(Visitor*);
 
@@ -96,10 +96,10 @@ public:
     DECLARE_VIRTUAL_TRACE();
 
     // WebRTCDataChannelHandlerClient
-    virtual void didChangeReadyState(WebRTCDataChannelHandlerClient::ReadyState) override;
-    virtual void didReceiveStringData(const WebString&) override;
-    virtual void didReceiveRawData(const char*, size_t) override;
-    virtual void didDetectError() override;
+    void didChangeReadyState(WebRTCDataChannelHandlerClient::ReadyState) override;
+    void didReceiveStringData(const WebString&) override;
+    void didReceiveRawData(const char*, size_t) override;
+    void didDetectError() override;
 
 private:
     RTCDataChannel(ExecutionContext*, RTCPeerConnection*, PassOwnPtr<WebRTCDataChannelHandler>);