Fix tree check for push-to-trunk.

This is a work-around simulating a --bypass-tree-check.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/136793005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18580 ce2b1a6d-e550-0410-aec6-3dcde31c8c00