Fix virtual/override/final usage in Source/core/{animation,css,style}/.

Source/core/css/CSSStyleRule.h

Index: Source/core/css/CSSStyleRule.h
diff --git a/Source/core/css/CSSStyleRule.h b/Source/core/css/CSSStyleRule.h
index bfd2924d078ca514fd5bc15b30f39e72714fa940..b66281d913eb30940a8e96a20c4d48face77bfff 100644
--- a/Source/core/css/CSSStyleRule.h
+++ b/Source/core/css/CSSStyleRule.h
@@ -39,10 +39,10 @@ public:
         return adoptRefWillBeNoop(new CSSStyleRule(rule, sheet));
     }
 
-    virtual ~CSSStyleRule();
+    ~CSSStyleRule() override;
 
-    virtual String cssText() const override;
-    virtual void reattach(StyleRuleBase*) override;
+    String cssText() const override;
+    void reattach(StyleRuleBase*) override;
 
     String selectorText() const;
     void setSelectorText(const String&);
@@ -57,7 +57,7 @@ public:
 private:
     CSSStyleRule(StyleRule*, CSSStyleSheet*);
 
-    virtual CSSRule::Type type() const override { return STYLE_RULE; }
+    CSSRule::Type type() const override { return STYLE_RULE; }
 
     String generateSelectorText() const;