Fix build failures with LLVM-GCC 4.2 on Mac.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/431613004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22716 ce2b1a6d-e550-0410-aec6-3dcde31c8c00