Fix clang compilation

BUG=none
TBR=svenpanne@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/621673003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24355 ce2b1a6d-e550-0410-aec6-3dcde31c8c00