Add explicit keyword to constructors that take one argument

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 56 matching lines @@
     bool isEmpty() const;
 
     virtual void registerForInvalidationCallbacks(FontSelectorClient*);
     virtual void unregisterForInvalidationCallbacks(FontSelectorClient*);
 
     Document* document() const { return m_document; }
 
     void beginLoadingFontSoon(FontResource*);
 
 private:
-    CSSFontSelector(Document*);
+    explicit CSSFontSelector(Document*);
 
     void dispatchInvalidationCallbacks();
 
     void beginLoadTimerFired(Timer<CSSFontSelector>*);
 
     Document* m_document;
     HashMap<String, OwnPtr<Vector<RefPtr<CSSFontFace> > >, CaseFoldingHash> m_fontFaces;
     HashMap<String, OwnPtr<Vector<RefPtr<CSSFontFace> > >, CaseFoldingHash> m_locallyInstalledFontFaces;
     HashMap<String, OwnPtr<HashMap<unsigned, RefPtr<CSSSegmentedFontFace> > >, CaseFoldingHash> m_fonts;
     HashSet<FontSelectorClient*> m_clients;
 
     Vector<ResourcePtr<FontResource> > m_fontsToBeginLoading;
     Timer<CSSFontSelector> m_beginLoadingTimer;
 
     unsigned m_version;
 };
 
 } // namespace WebCore
 
 #endif // CSSFontSelector_h