Fix virtual/override/final usage in Source/core/xml/.

Source/core/xml/DocumentXSLT.cpp

Index: Source/core/xml/DocumentXSLT.cpp
diff --git a/Source/core/xml/DocumentXSLT.cpp b/Source/core/xml/DocumentXSLT.cpp
index 99343a0d0e007a7bd463590e07aa4d3ac98c5664..58eb72fcd2f67f0f2ff377406d42f9edf00bb9ad 100644
--- a/Source/core/xml/DocumentXSLT.cpp
+++ b/Source/core/xml/DocumentXSLT.cpp
@@ -58,12 +58,12 @@ public:
         DocumentXSLT::applyXSLTransform(document, pi);
     }
 
-    virtual void detach() override
+    void detach() override
     {
         m_processingInstruction = nullptr;
     }
 
-    virtual EventListener* toEventListener() override
+    EventListener* toEventListener() override
     {
         return this;
     }
@@ -75,8 +75,8 @@ private:
     {
     }
 
-    virtual void refDetachableEventListener() override { ref(); }
-    virtual void derefDetachableEventListener() override { deref(); }
+    void refDetachableEventListener() override { ref(); }
+    void derefDetachableEventListener() override { deref(); }
 
     virtual v8::Local<v8::Value> callListenerFunction(ScriptState*, v8::Local<v8::Value>, Event*)
     {