This ensures that it'll be released on any control path leaving
the function thanks to desctuctor semantics.

BUG=42925

Review URL: http://codereview.chromium.org/1712025

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4554 ce2b1a6d-e550-0410-aec6-3dcde31c8c00