https://bugs.webkit.org/show_bug.cgi?id=113894

Reviewed by Mark Hahnenberg.

1) We previously had two different ways of convertingToForward, one path for
   where we had a ValueRecovery for the current node and one where we didn't.
   But the paths were doing exactly the same thing except that if you have a
   ValueRecovery, you also find the last applicable mov hint and do some
   extra things. This patch combines the two paths and bases both of them on
   the previous no-ValueRecovery path, which was simpler to begin with.

2) This moves the logic into DFG::OSRExit, which further simplifies the code
   and makes the logic available to the FTL.

* dfg/DFGOSRExit.cpp:
(JSC::DFG::OSRExit::convertToForward):
(DFG):
* dfg/DFGOSRExit.h:
(DFG):
(OSRExit):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::convertLastOSRExitToForward):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153114 268f45cc-cd09-0410-ab3c-d52691b4dbfc