This in preparation for C stack OSR entry work coming soon.
Created attachment 219354 [details] the patch. I'm applying this patch to trunk where I was able to test and validate it. Will merge it into the jsCStack branch after landing.
Thanks for the review. Landed in r160665: <http://trac.webkit.org/r160665>.
Merged into the jsCStack branch in r160666: <http://trac.webkit.org/r160666>.