Fix clang build.

See http://blog.llvm.org/2009/12/dreaded-two-phase-name-lookup.html.

TBR=rossberg@chromium.org

Review URL: https://codereview.chromium.org/134643025

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18756 ce2b1a6d-e550-0410-aec6-3dcde31c8c00