Use removeFontFace to avoid resetting fontSelector.

Source/core/css/CSSFontSelector.h

 /*
  * Copyright (C) 2007, 2008, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 72 matching lines @@
     // FontCacheClient implementation
     virtual void fontCacheInvalidated() OVERRIDE;
 
     void registerForInvalidationCallbacks(CSSFontSelectorClient*);
     void unregisterForInvalidationCallbacks(CSSFontSelectorClient*);
 
     Document* document() const { return m_document; }
     FontFaceCache* fontFaceCache() { return &m_fontFaceCache; }
 
     const GenericFontFamilySettings& genericFontFamilySettings() const { return m_genericFontFamilySettings; }
+    void updateGenericFontFamilySettings(Document&);
 
     void beginLoadingFontSoon(FontResource*);
     void loadPendingFonts();
 
 private:
     explicit CSSFontSelector(Document*);
 
     void dispatchInvalidationCallbacks();
 
     Document* m_document;
     // FIXME: Move to Document or StyleEngine.
     FontFaceCache m_fontFaceCache;
     HashSet<CSSFontSelectorClient*> m_clients;
 
     FontLoader m_fontLoader;
     GenericFontFamilySettings m_genericFontFamilySettings;
 };
 
 } // namespace WebCore
 
 #endif // CSSFontSelector_h