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

Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h

Index: Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h
diff --git a/Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h b/Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h
index c72c00a6c934e628304492ec396ed7e5898548c8..2e5b07324fa239155729110f4ab463136fa3ed43 100644
--- a/Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h
+++ b/Source/modules/mediastream/RTCSessionDescriptionRequestImpl.h
@@ -48,13 +48,13 @@ class RTCSessionDescriptionRequestImpl final : public RTCSessionDescriptionReque
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(RTCSessionDescriptionRequestImpl);
 public:
     static RTCSessionDescriptionRequestImpl* create(ExecutionContext*, RTCPeerConnection*, RTCSessionDescriptionCallback*, RTCErrorCallback*);
-    virtual ~RTCSessionDescriptionRequestImpl();
+    ~RTCSessionDescriptionRequestImpl() override;
 
-    virtual void requestSucceeded(const WebRTCSessionDescription&) override;
-    virtual void requestFailed(const String& error) override;
+    void requestSucceeded(const WebRTCSessionDescription&) override;
+    void requestFailed(const String& error) override;
 
     // ActiveDOMObject
-    virtual void stop() override;
+    void stop() override;
 
     DECLARE_VIRTUAL_TRACE();