Clean up virtual functions in css/

Source/core/css/LocalFontFaceSource.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LocalFontFaceSource_h
 #define LocalFontFaceSource_h
 
 #include "core/css/CSSFontFaceSource.h"
 #include "wtf/text/AtomicString.h"
 
 namespace blink {
 
-class LocalFontFaceSource : public CSSFontFaceSource {
+class LocalFontFaceSource final : public CSSFontFaceSource {
 public:
     LocalFontFaceSource(const String& fontName) : m_fontName(fontName) { }
-    virtual bool isLocal() const { return true; }
+    virtual bool isLocal() const override { return true; }
     virtual bool isLocalFontAvailable(const FontDescription&) override;
 
 private:
     virtual PassRefPtr<SimpleFontData> createFontData(const FontDescription&) override;
 
     class LocalFontHistograms {
     public:
         LocalFontHistograms() : m_reported(false) { }
         void record(bool loadSuccess);
     private:
         bool m_reported;
     };
 
     AtomicString m_fontName;
     LocalFontHistograms m_histograms;
 };
 
 } // namespace blink
 
 #endif