Add forced mode to push-to-trunk script.

This CL depends on https://codereview.chromium.org/65933003/.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/67763005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17893 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Quit running EnsureAllocationSiteDependentCodesProcessed test until
it's failure is diagnosed.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/77923002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17894 ce2b1a6d-e550-0410-aec6-3dcde31c8c00