Thread the Isolate through FindCodeInCache, FindCodeInSpecialCache and
SetProperty. Reduced the number of TLS accesses while running the Octane
benchmark down to 19% compared to the beginning of the cleanups.

Review URL: https://codereview.chromium.org/11411033

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13030 ce2b1a6d-e550-0410-aec6-3dcde31c8c00