Add explicit keyword to constructors that take one argument

Source/core/css/CSSImageGeneratorValue.h

 /*
  * Copyright (C) 2008 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 50 matching lines @@
 
     bool isFixedSize() const;
     IntSize fixedSize(const RenderObject*);
 
     bool isPending() const;
     bool knownToBeOpaque(const RenderObject*) const;
 
     void loadSubimages(ResourceFetcher*);
 
 protected:
-    CSSImageGeneratorValue(ClassType);
+    explicit CSSImageGeneratorValue(ClassType);
 
     Image* getImage(RenderObject*, const IntSize&);
     void putImage(const IntSize&, PassRefPtr<Image>);
     const RenderObjectSizeCountMap& clients() const { return m_clients; }
 
     HashCountedSet<IntSize> m_sizes; // A count of how many times a given image size is in use.
     RenderObjectSizeCountMap m_clients; // A map from RenderObjects (with entry count) to image sizes.
     HashMap<IntSize, RefPtr<Image> > m_images; // A cache of Image objects by image size.
 };
 
 } // namespace WebCore
 
 #endif // CSSImageGeneratorValue_h