Simplify and optimize String::format.

third_party/WebKit/Source/wtf/text/WTFString.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc.
  * All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 285 matching lines @@
   String simplifyWhiteSpace(IsWhiteSpaceFunctionPtr,
                             StripBehavior = StripExtraWhiteSpace) const;
 
   String removeCharacters(CharacterMatchFunctionPtr) const;
   template <bool isSpecialCharacter(UChar)>
   bool isAllSpecialCharacters() const;
 
   // Return the string with case folded for case insensitive comparison.
   String foldCase() const;
 
-  PRINTF_FORMAT(1, 2) static String format(const char*, ...);
+  // Takes a printf format and args and prints into a String.
+  PRINTF_FORMAT(1, 2) static String format(const char* format, ...);
 
   // Returns an uninitialized string. The characters needs to be written
   // into the buffer returned in data before the returned string is used.
   // Failure to do this will have unpredictable results.
   static String createUninitialized(unsigned length, UChar*& data) {
     return StringImpl::createUninitialized(length, data);
   }
   static String createUninitialized(unsigned length, LChar*& data) {
     return StringImpl::createUninitialized(length, data);
   }
@@ skipping 305 matching lines @@
 using WTF::String;
 using WTF::emptyString;
 using WTF::emptyString16Bit;
 using WTF::charactersAreAllASCII;
 using WTF::equal;
 using WTF::find;
 using WTF::isSpaceOrNewline;
 
 #include "wtf/text/AtomicString.h"
 #endif  // WTFString_h