https://bugs.webkit.org/show_bug.cgi?id=83546

Patch by Benjamin Poulain <bpoulain@apple.com> on 2012-04-11
Reviewed by Gavin Barraclough.

This patch adds a serie of optimizations to make stringProtoFuncSplit() faster in the common case
where the separator is a single character.

The two main gains are:
-Use of the find() function with a single character instead of doing a full string matching.
-Use of WTF::find() instead of UString::find() to avoid branching on is8Bit() and have a simpler inline
 function.

The code is also changed to avoid making unnecessary allocations by converting the 8bit string to 16bits.

This makes String.split() faster by about 13% in that particular case.

* runtime/StringPrototype.cpp:
(JSC):
(JSC::splitStringByOneCharacterImpl):
(JSC::stringProtoFuncSplit):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@113886 268f45cc-cd09-0410-ab3c-d52691b4dbfc