Update CSS classes to use OVERRIDE / FINAL when needed

Source/core/css/CSSStyleSheet.h

Index: Source/core/css/CSSStyleSheet.h
diff --git a/Source/core/css/CSSStyleSheet.h b/Source/core/css/CSSStyleSheet.h
index 1e063963f3e3c04cbc9725a2041d3d697310c069..f27a068c81f621129dbf9497cb8abae9fc274108 100644
--- a/Source/core/css/CSSStyleSheet.h
+++ b/Source/core/css/CSSStyleSheet.h
@@ -46,7 +46,7 @@ enum StyleSheetUpdateType {
     EntireStyleSheetUpdate
 };
 
-class CSSStyleSheet : public StyleSheet {
+class CSSStyleSheet FINAL : public StyleSheet {
 public:
     static PassRefPtr<CSSStyleSheet> create(PassRefPtr<StyleSheetContents>, CSSImportRule* ownerRule = 0);
     static PassRefPtr<CSSStyleSheet> create(PassRefPtr<StyleSheetContents>, Node* ownerNode);
@@ -114,8 +114,8 @@ private:
     CSSStyleSheet(PassRefPtr<StyleSheetContents>, CSSImportRule* ownerRule);
     CSSStyleSheet(PassRefPtr<StyleSheetContents>, Node* ownerNode, bool isInlineStylesheet, const TextPosition& startPosition);
 
-    virtual bool isCSSStyleSheet() const { return true; }
-    virtual String type() const { return "text/css"; }
+    virtual bool isCSSStyleSheet() const OVERRIDE { return true; }
+    virtual String type() const OVERRIDE { return "text/css"; }
 
     void reattachChildRuleCSSOMWrappers();