Speed up case folding for 8-bit strings

Source/wtf/text/StringHash.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2012, 2013 Apple Inc. All rights reserved
  * Copyright (C) Research In Motion Limited 2009. 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 108 matching lines @@
             return (a == b) || equal(a.impl(), b.impl());
         }
 
         static const bool safeToCompareToEmptyOrDeleted = false;
 
     private:
         // Private so no one uses this in the belief that it will return the
         // correctly-folded code point in all cases (see comment below).
         template<typename T> static inline UChar foldCase(T ch)
         {
+            if (IsSameType<T, LChar>::value)
+                return StringImpl::latin1CaseFoldTable[ch];
             // It's possible for WTF::Unicode::foldCase() to return a 32-bit
             // value that's not representable as a UChar.  However, since this
             // is rare and deterministic, and the result of this is merely used
             // for hashing, go ahead and clamp the value.
             return static_cast<UChar>(WTF::Unicode::foldCase(ch));
         }
     };
 
     // This hash can be used in cases where the key is a hash of a string, but we don't
     // want to store the string. It's not really specific to string hashing, but all our
@@ skipping 15 matching lines @@
         }
     };
 
 }
 
 using WTF::AlreadyHashed;
 using WTF::CaseFoldingHash;
 using WTF::StringHash;
 
 #endif