Fix ARM build on mac.

Remove a couple unused vars left behind after r16676. Clang on mac
is pickier than gcc on linux, specifically gcc does not complain about
unused class member variables.

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/39193003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17356 ce2b1a6d-e550-0410-aec6-3dcde31c8c00