This fixes recent performance regressions on Dromaeo.

BUG=chromium:242512
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/16226024

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14950 ce2b1a6d-e550-0410-aec6-3dcde31c8c00