Use removeFontFace to avoid resetting fontSelector.

Source/core/css/FontFaceCache.h

 /*
  * Copyright (C) 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google 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
@@ skipping 30 matching lines @@
 class StyleRuleFontFace;
 
 class FontFaceCache {
 public:
     FontFaceCache();
 
     // FIXME: Remove CSSFontSelector as argument. Passing CSSFontSelector here is
     // a result of egregious spaghettification in FontFace/FontFaceSet.
     void add(CSSFontSelector*, const StyleRuleFontFace*, PassRefPtr<FontFace>);
     void remove(const StyleRuleFontFace*);
+    void clear();
     void addFontFace(CSSFontSelector*, PassRefPtr<FontFace>, bool cssConnected);
     void removeFontFace(FontFace*, bool cssConnected);
 
     // FIXME: It's sort of weird that add/remove uses StyleRuleFontFace* as key,
     // but this function uses FontDescription/family pair.
     CSSSegmentedFontFace* get(const FontDescription&, const AtomicString& family);
 
     const ListHashSet<RefPtr<FontFace> >& cssConnectedFontFaces() const { return m_cssConnectedFontFaces; }
 
     unsigned version() const { return m_version; }
 
 private:
     typedef HashMap<unsigned, RefPtr<CSSSegmentedFontFace> > TraitsMap;
     typedef HashMap<String, OwnPtr<TraitsMap>, CaseFoldingHash> FamilyToTraitsMap;
     typedef HashMap<const StyleRuleFontFace*, RefPtr<FontFace> > StyleRuleToFontFace;
     FamilyToTraitsMap m_fontFaces;
     FamilyToTraitsMap m_fonts;
     StyleRuleToFontFace m_styleRuleToFontFace;
     ListHashSet<RefPtr<FontFace> > m_cssConnectedFontFaces;
 
     // FIXME: See if this could be ditched
     // Used to compare Font instances, and the usage seems suspect.
     unsigned m_version;
 };
 
 }
 
 #endif