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

Source/core/html/PluginDocument.h

Index: Source/core/html/PluginDocument.h
diff --git a/Source/core/html/PluginDocument.h b/Source/core/html/PluginDocument.h
index a77e113757d96757bb746230c7c99903ed3d7c71..ff772c6e3d87963621241780015e2ec13cc29c86 100644
--- a/Source/core/html/PluginDocument.h
+++ b/Source/core/html/PluginDocument.h
@@ -45,14 +45,14 @@ public:
     Widget* pluginWidget();
     Node* pluginNode();
 
-    virtual void detach(const AttachContext& = AttachContext()) override;
+    void detach(const AttachContext& = AttachContext()) override;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit PluginDocument(const DocumentInit&);
 
-    virtual PassRefPtrWillBeRawPtr<DocumentParser> createParser() override;
+    PassRefPtrWillBeRawPtr<DocumentParser> createParser() override;
 
     RefPtrWillBeMember<Node> m_pluginNode;
 };