Reduce forward declarations in core/rendering

Source/core/rendering/RenderThemeChromiumFontProvider.h

 /*
  * Copyright (C) 2012 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef RenderThemeChromiumFontProvider_h
 #define RenderThemeChromiumFontProvider_h
 
 #include "core/CSSValueKeywords.h"
 
-namespace WTF {
-class String;
-}
-
 namespace WebCore {
 
 class FontDescription;
 
 class RenderThemeChromiumFontProvider {
 public:
     static void systemFont(CSSValueID, FontDescription&);
     static void setDefaultFontSize(int);
 
 protected:
     static const WTF::AtomicString& defaultGUIFont();
 
     static float s_defaultFontSize;
 };
 
 } // namespace WebCore
 
 #endif // RenderThemeChromiumFontProvider_h