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

Source/web/ExternalDateTimeChooser.cpp

Index: Source/web/ExternalDateTimeChooser.cpp
diff --git a/Source/web/ExternalDateTimeChooser.cpp b/Source/web/ExternalDateTimeChooser.cpp
index fc2cfc3f3e552c50a2e2e806fbe096177fa0acb4..b609d71bea0134cef862b172e19064f899ab4845 100644
--- a/Source/web/ExternalDateTimeChooser.cpp
+++ b/Source/web/ExternalDateTimeChooser.cpp
@@ -45,19 +45,19 @@ public:
     }
 
 private:
-    virtual void didChooseValue(const WebString& value) override
+    void didChooseValue(const WebString& value) override
     {
         m_chooser->didChooseValue(value);
         delete this;
     }
 
-    virtual void didChooseValue(double value) override
+    void didChooseValue(double value) override
     {
         m_chooser->didChooseValue(value);
         delete this;
     }
 
-    virtual void didCancelChooser() override
+    void didCancelChooser() override
     {
         m_chooser->didCancelChooser();
         delete this;