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

Source/core/css/CSSImportRule.h

Index: Source/core/css/CSSImportRule.h
diff --git a/Source/core/css/CSSImportRule.h b/Source/core/css/CSSImportRule.h
index eb49fdad9ccefa89b30f188ad5d49cf38ac03c73..64c357c9e191d07f5ed6febe6e4a95b4550cdaea 100644
--- a/Source/core/css/CSSImportRule.h
+++ b/Source/core/css/CSSImportRule.h
@@ -38,10 +38,10 @@ public:
         return adoptRefWillBeNoop(new CSSImportRule(rule, sheet));
     }
 
-    virtual ~CSSImportRule();
+    ~CSSImportRule() override;
 
-    virtual String cssText() const override;
-    virtual void reattach(StyleRuleBase*) override;
+    String cssText() const override;
+    void reattach(StyleRuleBase*) override;
 
     String href() const;
     MediaList* media() const;
@@ -52,7 +52,7 @@ public:
 private:
     CSSImportRule(StyleRuleImport*, CSSStyleSheet*);
 
-    virtual CSSRule::Type type() const override { return IMPORT_RULE; }
+    CSSRule::Type type() const override { return IMPORT_RULE; }
 
     RefPtrWillBeMember<StyleRuleImport> m_importRule;
     mutable RefPtrWillBeMember<MediaList> m_mediaCSSOMWrapper;