Speed up case folding for 8-bit strings

Source/wtf/text/StringHash.h

Index: Source/wtf/text/StringHash.h
diff --git a/Source/wtf/text/StringHash.h b/Source/wtf/text/StringHash.h
index 3b54b7a9fe4708a00a9bfe9e5104588e6f728814..a5bb00cf0e3b1f0b970465bd2375f916d0c308a3 100644
--- a/Source/wtf/text/StringHash.h
+++ b/Source/wtf/text/StringHash.h
@@ -126,6 +126,8 @@ namespace WTF {
         // 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